Original Article PeriPaPillary and Macular nerve fiber layer thickness in GlaucoMa J Nepal Paediatr Soc | VOL 42 | ISSUE 02 |MAY-AUG, 202230 *Pragati Adhikari Gautam1, Hira Nath Dahal2, Jyoti Baba Shrestha3 1Lecturer, Department of Ophthalmology, B P Koirala Lions Center for Ophthalmic Studies, Maharajgunj Medical Campus, Tribhuvan University, Kathmandu, Nepal 2Optomtery Instructor, Department of Ophthalmology, B P Koirala Lions Center for Ophthalmic Studies, Maharajgunj Medical Campus, Tribhuvan University, Kathmandu, Nepal 3Associate Professor, Department of Ophthalmology, B P Koirala Lions Center for Ophthalmic Studies, Maharajgunj Medical Campus, Tribhuvan University, Kathmandu, Nepal Evaluation of Peripapillary and Macular Nerve Fiber Layer Thickness in Paediatric Glaucoma Suspects Introduction: Glaucoma patients are known to have optic disc cupping, leading to loss of retinal ganglion cell axons. This peripapillary nerve thinness is known to be associated with glaucoma in adult patients. Hence, we intended to evaluate the peripapillary and macular nerve fiber thickness in eyes of pediatric glaucoma suspects using spectral domain optical coherence tomography (OCT). Methods: This cross-sectional analytical study included 44 eyes of 22 paediatric glaucoma suspects, who were compared with 40 eyes of 20 normal paediatric eyes. Pearson correlation coefficients were calculated to assess the relations between the peripapillary retinal nerve fiber layer (RNFL) thickness and ganglion cell complex (GCC). Receiver Operating Characteristics (ROC) curve was plotted for OCT parameters in both the groups along with area under the curve (AUC) calculation. P values < 0.05 were considered as statistically significant. Results: We found the RNFL to be thickest in the superior, inferior, nasal and temporal quadrants in both glaucoma suspects and normal group. When compared among quadrants in RNFL, all the values in different quadrants were statistically significant from each other and in between groups with p < 0.01. The RNFL thickness was statistically different in glaucoma when compared with normal in superior, temporal, and nasal quadrants however, no statistically significant difference was found in inferior quadrant RNFL. The largest AUC for discrimination of glaucoma suspect eyes from normal in peripapillary RNFL in was nasal quadrant in right eye, followed by temporal quadrant whereas it was largest in superior followed by nasal quadrants then average in left eye. However, AUC for discrimination of glaucoma suspects from normal in GCC was poor. Conclusions: Glaucoma suspect paediatric eyes showed significant thinning in peripapillary nerve fiber layer thickness compared to normal subjects. Abstract *Corresponding Author Pragati Gautam Adhikari Lecturer, Department of Ophthalmology, B P Koirala Lions Center for Ophthalmic Studies, Maharajgunj Medical Campus, Maharajgunj, Kathmandu, Nepal. E-mail: pragatigautam@hotmail.com Article History Received On : 18 Jan, 2022 Accepted On : 09 Dec, 2022 Funding sources: None Conflicts of interest: None Keywords: Ganglion cell complex; Pediatric glaucoma; Retinal nerve fiber layer; Spectral domain OCT Online Access DOI: https://doi.org/10.3126/jnps.v42i2.42495 Introduction Glaucomatous optic disc cupping is associated with the loss of retinal ganglion cell axons.1 Normal optic disc usually has the inferior neuroretinal rim as the thickest portion of the rim, followed by the superior rim, and then the nasal rim, with the temporal rim being the thinnest portion.2 Violation of this ISNT rule has shown to have predictive value in diagnosing glaucoma in adults.3,4 Original Article DOI: 103126/JNPS.V4113 Copyrights & Licensing © 2022 by author(s). This is an Open Access article distribut- ed under Creative Commons Attribution License (CC BY NC ) J Nepal Paediatr Soc | VOL 42 | ISSUE 02 |MAY-AUG, 2022 31 Original ArticlePeriPaPillary and Macular nerve fiber layer thickness in GlaucoMa The faster image acquisition with spectral-domain OCT (SD - OCT) like RTVue has made OCT even more feasible in children.5-9 OCT has been used in eyes of normal children but published reports of the use of OCT in paediatric glaucoma suspects are sparse. This study tries to explore and correlate the measurements of peripapillary RNFL thickness and macular thickness in paediatric glaucoma suspects with that of normal using SD - OCT. To the best of our knowledge, this is one of the first studies using the OCT machine to investigate the correlation between the macular thickness and the peripapillary RNFL thickness in pediatric glaucoma and suspects. Methods This was a hospital-based cross-sectional comparative study. Written informed consent was obtained from all parents or guardians. Approval from the Institutional Review Committee of Institute of Medicine was taken. The study duration was from 15th June 2021 to 15th December 2021. From a prevalence of childhood glaucoma from previous study done in Nepal,9 a sample size of 22 was calculated for glaucoma suspects and 20 cases were taken in for control. The non-probability purposive sampling method was applied. Children aged between five to 17 years with glaucoma suspect were included in study. Children less than five years, those with hypermetropia more than + 3D, myopia more than – 5D, or astigmatism more than 2D, pseudophakia and prematurity at birth, corneal lesions, chronic uveitis, secondary glaucoma, optic neuropathy other than glaucoma, retinal pathology, maculopathy and previous ocular trauma history were excluded from this study. The peripapillary retinal nerve fiber layer (RNFL) and macular thickness mainly ganglion cell complex (GCC) was compared amongst two groups: normal eyes, eyes with glaucoma suspects. Glaucoma suspects were defined as eyes with (cup disc ratio < 0.4 and < 0.7, IOP < 21), with or without family history of glaucoma, vertical cup-to-disc ratio asymmetry < 0.2 between the two eyes without focal notching or generalized loss of the neuroretinal rim, excavation of the optic disc was taken as glaucoma suspects. The normal subjects were from patients coming for routine ophthalmic examination, with no clinical suspicion of glaucoma, who also had optic nerves and retinas that were considered clinically normal. Family history in these individuals was negative for glaucoma. All subjects underwent a complete ophthalmological examination. The intraocular pressure (IOP) was measured with Keeler, UK pulse air desktop non-contact applanation tonometry and any high reading < = 21 were be reconfirmed with Goldman applanation tonometry. For peripapillary RNFL and Ganglion cell complex in macular thickness measurements the RTVue -100 software was used. Peripapillary RNFL thickness measurements were performed by the same investigator using RTVue OCT (Optovue, Fremont, CA). The RNFL thickness was measured by averaging the results of three sequential circular scans. Images with signal strength index ≥ 50 were included in the study. Both eyes from each individual were included in the analyses. The statistical package for social sciences (SPSS) version 22.0 was used in the analysis. Pearson correlation coefficients were calculated to assess the relations between the peripapillary RNFL thickness and GCC. Interocular OCT parameters difference among gender was calculate with paired t test. Interocular OCT parameters difference was calculated with paired t test among glaucoma suspects and control. The OCT parameters were compared among the two groups by one-way ANOVA test. Receiver Operating Characteristics (ROC) curve was plotted for OCT parameters in both control and glaucoma suspect along with area under the curve (AUC) calculation. The diagnostic specificity and sensitivity of the main parameters (AUC < 0.7) for distinguishing fellow eyes from normal eyes were evaluated, and cut-off points were presented. A probability value (P value) less than 0.05 was considered as significant at 95% confidence level. Results The mean age of the subjects in the study was 14.59 ± 1.89 years (11 years - 17 years). Of the total 22 subjects in the study, 54.5% (n = 12) were males and 45.5% (n = 10) were females. The mean cup disc ratio was 0.56 ± 0.078 in right eyes and 0.55 ± 0.071 in left eyes. Twenty age and gender matched normal children were also included in the study. The mean age of normal group was 13.80 ± 2.14 years (11 - 17 years). Male to female ratio was 1:1 in control group. All subjects had best corrected visual acuities of 0.0 logMAR or better. None of subjects had glaucoma, ocular hypertension. There was no effect of age on RNFL thickness in glaucoma suspects and normal as presented in Table 1. Average OCT parameters were not statistically significant in relation to gender (RE, p = 0.630, LE p = 0.178, independent t - test) in glaucoma suspect group. Original Article PeriPaPillary and Macular nerve fiber layer thickness in GlaucoMa J Nepal Paediatr Soc | VOL 42 | ISSUE 02 |MAY-AUG, 202232 Table 1. OCT parameters in relation to gender OCT Parameters (µm) Male Female P value (Independent t-test) Right Eye Superior 22.77 ± 130 16.15 ± 129.60 0.876 Inferior 24.05 ± 127.83 14.54 ± 121.00 0.422 Temporal 12.39 ± 75.75 7.43 ± 72.70 0.485 Nasal 12.50 ± 74.66 12.77 ± 82.10 0.186 Average 17.48 ± 104.37 11.26 ± 101.35 0.630 Left Eye Superior 13.36 ± 133.33 12.73 ± 124.10 0.114 Inferior 18.77 ± 128.91 15.74 ± 120.00 0.240 Temporal 8.14 ± 77.50 8.52 ± 71.30 0.099 Nasal 8.80 ± 76.66 11.00 ± 79.20 0.564 Average 9.24 ± 104.10 9.02 ± 98.65 0.178 In this study, we found RNFL to be thickest in the superior, inferior, nasal and temporal quadrants, in that order in both glaucoma suspects and control group. When compared among quadrants in RNFL, all the values in different quadrant were statistically sig- nificant from each other and in between groups with p < 0.01 when tested with ANOVA test. This means, there was statistically significant difference in RNFL thickness quadrant wise and in be- tween groups. RNFL thickness was statistically different in glauco- ma suspects when compared with control in superior, temporal, and nasal quadrants as presented in Table 2. Table 2. Intraocular differences in peri papillary nerve fiber thickness along different quadrant OCT characteristics (µm) Right Eye P value (ANOVA) Left Eye P value (ANOVA)Glaucoma Suspects Normal Glaucoma Suspects Normal Superior 19.59 ± 130.31 142.31±7.10 0.005 13.60 ± 129.13 6.22 ± 144.60 0.000 Inferior 20.14 ± 124.72 9.73 ± 124.72 0.680 17.65 ± 124.86 8.60 ± 126.10 0.744 Temporal 22.79 ± 78.90 4.75 ± 82.80 0.002 8.70 ± 74.68 5.77 ± 82.40 0.005 Nasal 12.89 ± 78.04 9.73 ± 93.20 0.000 9.70 ± 77.81 10.22 ± 90.30 0.000 Average 14.72 ± 103.00 6.14 ± 110.85 0.019 9.34 ± 101.62 6.44 ± 110.85 0.001 The macular ganglion cell complex thickness was similar in both groups with no statically significant difference quadrant wise in both right eye and left eye respectively. (Table 3) Table 3. Distribution of macular ganglion cell thickness Ganglion cell thickness (µm) Right Eye P value (ANOVA) Left Eye P value (ANOVA) Glaucoma Suspects Normal Glaucoma Suspects Normal Superior quadrant 12.20 ± 94.50 2.68 ± 95.10 0.648 7.08 ± 94.59 3.78 ± 93.10 0.458 Inferior quadrant 10.45 ± 93.68 3.22 ± 95.20 0.296 6.83 ± 94.90 3.52 ± 92.70 0.291 Average 10.98 ± 94.09 2.92 ± 95.15 0.460 6.69 ± 94.75 3.58 ± 92.9 0.349 However, there was no statistically significant interocular difference quadrant wise in right eye and left eye respectively. (Table 4) J Nepal Paediatr Soc | VOL 42 | ISSUE 02 |MAY-AUG, 2022 33 Original ArticlePeriPaPillary and Macular nerve fiber layer thickness in GlaucoMa Table 4. Comparison between mean peri-papillary nerve fiber thickness between right eye and left eye in glaucoma suspect group Quadrant Right Eye Left Eye P value (t-test) Superior 19.59 ± 130.31 13.60 ± 129.13 0.765 Inferior 20.14 ± 124.72 17.65 ± 124.86 0.972 Temporal 22.79 ± 78.90 8.70 ± 74.68 0.887 Nasal 12.89 ± 78.04 9.70 ± 77.81 0.926 Average 14.72 ± 103.00 9.34 ± 101.62 0.584 The peri-papillary RNFL in all quadrants showed a positive correlation with GCC in right eyes whereas no such correlation was found in left eyes and in both eyes of control group. Pearson correlation coefficients among the different quadrants to that of GCC displayed significant correlation with that of all quadrants and average parameters in right eye and only superior quadrant in left eye in glaucoma suspect group. (Table 5) Table 5. Correlation between peri papillary nerve fiber thickness and average macular ganglion cell thickness (Pearson Correlation) Glaucoma Suspect Control Quadrant (GCC (RE (GCC (LE (GCC (RE (GCC (LE Superior (r = 0.755, p = 0.000) (r = 0.410, p = 0.058) (r = 0.343, p = 0.331) (r = 0.371, p = 0.291) Inferior (r = 0.587, p = 0.004) (r = 0.077, p = 0.734) (r = -0.177, p=0.625) (r = -0.066, p = 0.856) Temporal (r = 0.785, p = 0.000) (r = 0.252, p = 0.257) (r = 0.314, p = 0.377) (r = -0.100, p = 0.784) Nasal (r = 551, p = 0.008) (r = 0.392, p = 0.071) (r = -0.256, p = 0.475) (r = -0.228, p = 0.527) Average (r = 0.658, p = 0.001) (r = 0.346, p = 0.115) (r = -0.007, p = 0.984) (r = -0.045, p = 0.901) ROC curves were plotted and AUC calculated for right eye and left eye for RNFL thickness and GCC thickness respectively. The largest AUC for discrimination of glaucoma suspect eyes from normal in peripapillary RNFL in was nasal quadrant (0.84) in right eye, followed by temporal quadrant (0.78) whereas it was largest in superior (0.85) followed by nasal quadrants (0.83) then average (0.80) in left eye. This was statistically significant to diagnose glaucoma suspects from normal eye. However, AUC for discrimination of glaucoma suspects from normal in GCC was poor in right eye (0.54) and had no discrimination in left eye (0.38). Discussion The present study showed that average peripapillary RNFL and peripapillary RNFL of all sectors except for inferior was significantly thinner in glaucoma suspects compared to normal children. Since glaucomatous optic neuropathy has been documented to develop locally rather than globally3 The normal group of participants had thicker RNFL using SD-OCT as compared to earlier studies,3,4 with maximum thickness in the superior quadrant, contradicting the ISNT rule. Some researchers have reported the thinning of average RNFL thickness in all sectors between paediatric glaucoma and controls. However, other researchers have found that children with glaucoma and normal participants have comparable RNFL thickness in some regions such as the temporal, nasal, and inferior nasal quadrants. The average peripaillary thickness was 110.85 ± 6.14 in right eyes and 110.85 ± 6.44 in left eyes in normal group which is slightly higher than reported in various studies11-14 but almost similar to reported in others.15-17 This may be attributed to ethnic differences and differences in the OCT version used in earlier studies. Studies of the sensitivity and specificity of OCT for the diagnosis of glaucoma have primarily focused on glaucoma patients who already have visual field defects.18,19 However, in our study, the largest AUC for discrimination of glaucoma suspect eyes from normal in peripapillary RNFL in was nasal quadrant in right eye, followed by temporal quadrant whereas it was largest in superior followed by nasal quadrants then average in left eye. Budenz and associates found higher AUC values for mean RNFL thickness, superior quadrant and inferior quadrant.8 Similarly, in a study comparing SD-OCT to stratus OCT, the RNFL parameters with the highest AUCs were in similar locations as those in the Stratus OCT.20 The ability to discriminate normal from glaucomatous results is directly proportional to the magnitude of disease severity as suggested in previous studies.19,21,22 The changes of pRNFL thickness are meaningful in these children with less severe glaucomatous optic nerve damage, where the damage of visual function may be difficult to measure. Age-related decrease in RNFL has been reported in adults11,23 using OCT however it was not found in our study of paediatric age group. Similar to our finding, Rao et al also showed that peripapillary RNFL thickness was independent of age in children.24 Alamouti and Funk have suggested that the rate of decrease in RNFL thickness is slower in the younger age.23 However, it is still unclear as to the exact age at which the thinning starts. More so, it is possible that such an age-related process starts in adult life, which may explain the lack Original Article PeriPaPillary and Macular nerve fiber layer thickness in GlaucoMa J Nepal Paediatr Soc | VOL 42 | ISSUE 02 |MAY-AUG, 202234 of correlation of age with RNFL thickness in the paediatric group.24 Gender also did not contribute to the variability in RNFL thickness in our study. Similarly, such gender related difference in the pediatric age group was not found in other studies too.25,26 In our study, we did not find significant differences between the two eyes with symmetric RNFL and macular parameters. Similarly, no significant difference in mean RNFL thickness of the four quadrants was seen between the two eye in other studies.7,24 However, eye side had significant influence on RNFL thickness in some studies.8,10,13 The mechanism underlying interocular differences is unclear in normal children, it may be physiological however in children with glaucoma suspects or glaucoma it could be attributed to the asymmetrical nature of the disease itself. In addition to peripapillary RNFL thickness, macular thickness especially GCC has been shown as an important parameter for the early detection of glaucoma in adults, with significant differences reported by some between glaucomatous and normal eyes. In the study by Hess et al, significant differences were found in the OCT scans obtained from glaucoma patients compared with those of normal children, using both the RNFL map protocol and the fast macular map.27 However, another study has showed that macular thickness had lower diagnostic capability compared with peripapillary RNFL thickness in early glaucoma.19 Similarly, no much difference was found in our study too. Since diagnostic accuracy of GCC is significantly influenced by disease severity. Moreso, this difference may not be pronounced in early disease state. Our group of glaucoma suspect eyes based on optic nerve cupping. Even though we did not correlate RNFL and cupping, a study had correlated RNFL and cupping and found that the degree of optic nerve cupping does not correlate with the RNFL thickness.10 The glaucoma suspects patients may represent a mild or early stage of glaucomatous damage. This provides us with a standard comparison for glaucoma screening since any deviation from the normative database would be definite along with other factors. Inclusion of eyes with glaucoma in the group would probably have made the differences between the glaucoma and normal groups even larger. The axial length was not taken into account in our study and our measurements were obtained in children without ocular disease and significant refractive error as previous studies showed that they did not affect the RNFL and GCC parameters significantly.13,15 The strength of the study is that it included a heterogeneous mixture of Nepalese ethnic group visiting a tertiary eye care center in Kathmandu, Nepal. The major limitation of the present study is related to the characteristics of the subjects enrolled ranging mainly in age group 11 - 17 years, so results may not be applicable to younger age groups. More so, a larger sample size will help to differentiate better predictive value of each parameter. Longitudinal follow-up of eyes with paediatric glaucoma suspects, and serial OCT measurements in these same eyes, will assess the use of this technology in monitoring glaucoma progression and evaluate outcomes in more detail along with identification of additional risk factors in the development of glaucoma in paediatric glaucoma suspects. Conclusions This study demonstrated that spectral domain OCT of RNFL can quantitatively measure structural changes that are known to occur with glaucoma, in glaucoma suspects. In our study, paediatric glaucoma suspects had significantly reduced average quadrants RNFL thickness compared with healthy controls along with largest AUC for discrimination of glaucoma suspect eyes from normal in nasal quadrant and temporal quadrant in right eye, and superior, nasal quadrants and average RNFL in left eye. We would like to highlight SD-OCT has potential clinical value in early diagnosis in pediatric glaucoma suspects. References 1. Zhang YX, Huang HB, Wei SH. Clinical characteristics of nonglaucomatous optic disc cupping. Exp Ther Med. 2014;7(4):995-9. DOI: https://doi.org/10.3892/etm.2014.1508 2. Jonas JB, Gusek GC, Naumann GO. Optic disc, cup and neuroretinal rim size, configuration and correlations in normal eyes. Invest Ophthalmol Vis Sci. 1988;29(7):1151-8. 3. Jonas JB, Fernández MC, Stürmer J. Pattern of glaucomatous neuroretinal rim loss. Ophthalmology. 1993;100(1):63-8. DOI: https://doi.org/10.1016/s0161-6420(13)31694-7 4. Harizman N, Oliveira C, Chiang A, Tello C, Marmor M, Ritch R, et al. The ISNT rule and differentiation of normal from glaucomatous eyes. Arch Ophthalmol. (Chicago, Ill : 1960). 2006;124(11):1579-83. DOI: https://doi.org/10.1001/archopht.124.11.1579 5. Vonor K, Kuaovi Koko RA, Santos M, Ayéna KD, Amédomé KM, Dzidzinyo K, et al. [Role of SD-OCT in pediatric glaucoma suspects]. J Fr Ophtalmol. 2015;38(10):e235-6. DOI:https://doi.org/10.1016/j.jfo.2014.09.030 6. Pazos M, Biarnés M, Blasco-Alberto A, Dyrda A, Luque- Fernández M, Gómez A, et al. SD-OCT peripapillary nerve fibre layer and ganglion cell complex parameters in glaucoma: principal component analysis. Br J Ophthalmol. 2021;105(4):496-501. DOI: https://doi.org/10.1136/bjophthalmol-2020-316296 7. Ahn HC, Son HW, Kim JS, Lee JH. Quantitative analysis of retinal nerve fiber layer thickness of normal children and adolescents. Korean J Ophthalmol. 2005;19(3):195-200. DOI:https://doi.org/10.3341/kjo.2005.19.3.195 8. Budenz DL, Anderson DR, Varma R, Schuman J, Cantor L, Savell J, et al. Determinants of normal retinal nerve fiber layer thickness measured by Stratus OCT. Ophthalmology. 2007;114(6):1046-52. DOI: https://doi.org/10.1016/j.ophtha.2006.08.046 9. Shakya S KS, Pradhan E. Pattern of Childhood Glaucoma. J Nepal Med Assoc. 2013;39(144):4. DOI: https://doi.org/ https://doi.org/10.31729/jnma.679 J Nepal Paediatr Soc | VOL 42 | ISSUE 02 |MAY-AUG, 2022 35 Original ArticlePeriPaPillary and Macular nerve fiber layer thickness in GlaucoMa 10. Gherghel D, Orgül S, Prünte C, Gugleta K, Lübeck P, Gekkieva M, et al. Interocular differences in optic disc topographic parameters in normal subjects. Curr Eye Res. 2000;20(4):276-82 11. Parikh RS, Parikh SR, Sekhar GC, Prabakaran S, Babu JG, Thomas R. Normal age-related decay of retinal nerve fiber layer thickness. Ophthalmology. 2007;114(5):921-6. DOI: https://doi.org/10.1016/j.ophtha.2007.01.023 12. Gupta G, Donahue JP, You T. Profile of the retina by optical coherence tomography in the pediatric age group. Am J Ophthalmol. 2007;144(2):309-10. DOI: https://doi.org/10.1016/j.ajo.2007.03.029 13. Huynh SC, Wang XY, Rochtchina E, Crowston JG, Mitchell P. Distribution of optic disc parameters measured by OCT: findings from a population-based study of 6-year-old Australian children. Invest Ophthalmol Vis Sci. 2006;47(8):3276-85. DOI: https://doi.org/10.1167/iovs.06-0072 14. Larsson E, Molnar A, Holmström G. Repeatability, reproducibility and interocular difference in the assessments of optic nerve OCT in children- a Swedish population-based study. BMC Ophthalmol. 2018;18(1):270. DOI: https://doi.org/10.1186/s12886-018-0940-x 15. El-Dairi MA, Asrani SG, Enyedi LB, Freedman SF. Optical coherence tomography in the eyes of normal children. Arch Ophthalmol (Chicago, Ill : 1960). 2009;127(1):50-8. DOI: https://doi.org/10.1001/archophthalmol.2008.553 16. Tsai DC, Huang N, Hwu JJ, Jueng RN, Chou P. Estimating retinal nerve fiber layer thickness in normal schoolchildren with spectral-domain optical coherence tomography. Japanese journal of ophthalmology. 2012;56(4):362-70. DOI: https://doi.org/10.1007/s10384-012-0142-7 17. Repka MX, Goldenberg-Cohen N, Edwards AR. Retinal nerve fiber layer thickness in amblyopic eyes. Am J Ophthalmol. 2006;142(2):247-51. DOI: https://doi.org/10.1016/j.ajo.2006.02.030 18. Shah NN, Bowd C, Medeiros FA, Weinreb RN, Sample PA, Hoffmann EM, et al. Combining structural and functional testing for detection of glaucoma. Ophthalmology. 2006;113(9):1593-602. DOI: https://doi.org/10.1016/j.ophtha.2006.06.004 19. Parikh RS, Parikh S, Sekhar GC, Kumar RS, Prabakaran S, Babu JG, et al. Diagnostic capability of optical coherence tomography (Stratus OCT 3) in early glaucoma. Ophthalmology. 2007;114(12):2238-43. DOI: https://doi.org/10.1016/j.ophtha.2007.03.005 20. Ghasia FF, Freedman SF, Rajani A, Holgado S, Asrani S, El-dairi M. Comparison of stratus and spectralis optical coherence tomography (oct) in pediatric glaucoma evaluation. Journal of American Association for Pediatric Ophthalmology and Strabismus {JAAPOS}. 2012;16(1):e17. DOI: https://doi.org/10.1016/j.jaapos.2011.12.065 21. Sehi M, Grewal DS, Sheets CW, Greenfield DS. Diagnostic ability of Fourier-domain vs time-domain optical coherence tomography for glaucoma detection. Am J Ophthalmol. 2009;148(4):597-605. DOI: https://doi.org/10.1016/j.ajo.2009.05.030 22. Wu H, de Boer JF, Chen TC. Diagnostic capability of spectral- domain optical coherence tomography for glaucoma. Am J Ophthalmol. 2012;153(5):815-26.e2. DOI: https://doi.org/10.1016/j.ajo.2011.09.032 23. Alamouti B, Funk J. Retinal thickness decreases with age: an OCT study. Br J Ophthalmol. 2003;87(7):899-901. DOI: https://doi.org/10.1136/bjo.87.7.899 24. Rao A, Sahoo B, Kumar M, Varshney G, Kumar R. Retinal nerve fiber layer thickness in children <18 years by spectral- domain optical coherence tomography. Semin Ophthalmol. 2013;28(2):97-102. DOI: https://doi.org/10.3109/08820538.2012.760626 25. Salchow DJ, Oleynikov YS, Chiang MF, Kennedy-Salchow SE, Langton K, Tsai JC, et al. Retinal nerve fiber layer thickness in normal children measured with optical coherence tomogra- phy. Ophthalmology. 2006;113(5):786-91. DOI: https://doi.org/10.1016/j.ophtha.2006.01.036 26. Pawar N, Maheshwari D, Ravindran M, Ramakrishnan R. Interocular symmetry of retinal nerve fiber layer and optic nerve head parameters measured by Cirrus high-definition optical coherence tomography in a normal pediatric population. Indian J Ophthalmol. 2017;65(10):955-62. DOI: https://doi.org/10.4103/ijo.IJO_71_17 27. Hess DB, Asrani SG, Bhide MG, Enyedi LB, Stinnett SS, Freed- man SF. Macular and retinal nerve fiber layer analysis of nor- mal and glaucomatous eyes in children using optical coher- ence tomography. Am J Ophthalmol. 2005;139(3):509-17. DOI: https://doi.org/10.1016/j.ajo.2004.10.047