Optic Disc Area Research Articles

Myopic Optic Disc Tilt and the Characteristics of Peripapillary Retinal Nerve Fiber Layer Thickness Measured by Spectral-domain Optical Coherence Tomography

To investigate the correlation between myopic optic disc tilt and the characteristics of peripapillary retinal nerve fiber layer (RNFL) thickness measured by Cirrus HD spectral-domain optical coherence tomography (Cirrus HD OCT; Carl Zeiss Meditec, Dublin, CA). A total of 255 eyes of 255 healthy young male participants with various degrees of refractive errors (mean spherical equivalent, -3.17 ± 2.40 D; range, -11.00 to 0.00 D) underwent ophthalmic examinations, including refractive error, axial length, and optic disc area measurement. The degree of horizontal/vertical optic disc tilt was evaluated by cross-sectional images obtained by the Cirrus HD OCT. The average, superior, nasal, inferior, and temporal quadrant thickness and superior/inferior peak locations of the peripapillary RNFL were also measured with the Cirrus HD OCT. On the univariate analysis, eyes with more temporally tilted optic discs (horizontal tilt) had higher myopia, greater axial length, a thinner average, superior, nasal, and inferior RNFL, thicker temporal RNFL, and more temporally positioned superior/inferior peak locations (all P values <0.001). The degree of inferior optic disc tilt (vertical tilt) was associated with high myopia and a more temporally positioned inferior peak location (all P values <0.05). On multivariate analysis, eyes with more temporally tilted optic discs had a thicker temporal RNFL and more temporally positioned superior/inferior peak locations. The characteristics of the peripapillary RNFL thickness were associated with the degree of myopic optic disc tilt, especially in the temporal area. The degree of myopic optic disc tilt should be considered when interpreting the RNFL thickness measured by the Cirrus HD OCT.

Estudo das correlações entre a área do disco óptico e as características geométricas e biomecânicas da córnea

PURPOSE: To correlate optic disc size geometry, corneal architecture and biomechanics. METHODS: Optic disc area and geometry was accessed by HRT III (Heidelberg Retina Tomography – Heidelberg eng), Pentacam (Oculus) was used for accessing IOP and corneal parameters and ORA (Ocular Response Analyze – Reichert) was utilized to access corneal biomechanical properties. Classification based DDLS (Disc Damage Likelihood Scale) scale from retinography was performed. Settings: Instituto de Olhos Renato Ambrósio. RESULTS: 244 eyes of 122 patients (75 female) were included. [...]

Macular and Retinal Nerve Fiber Layer Thickness: Which Is More Helpful in the Diagnosis of Glaucoma?

To explore factors affecting the glaucoma diagnostic capability of macular thickness and circumpapillary retinal nerve fiber layer (cRNFL) thickness as determined by spectral domain-optical coherence tomography. Area under the curve (AUC) of the receiver operating characteristics (ROC) discriminating healthy from glaucomatous eyes was determined using 10 macular thickness and 16 cRNFL thickness parameters. Glaucomatous eyes were categorized into two groups using four criteria according to whether cRNFL thickness or macular thickness measurement was better for glaucoma detection (cRNFL better group [RBG], macula better group [MBG], respectively). The clinical characteristics were compared between RBG and MBG. ROC regression analysis was conducted to identify variables affecting diagnostic capability using either macular thickness or cRNFL thickness measurements. Four hundred twenty-four glaucomatous patients and 297 healthy subjects were analyzed. Of all cRNFL parameters, average thickness showed the largest AUC (0.958). Of macular parameters, the inferior outer sector showed the largest AUC (0.880). More eyes were placed into the RBG than the MBG, making use of all four criteria (90 vs. 24, 143 vs. 46, 76 vs. 18, and 103 vs. 36, respectively). RBG patients had a smaller optic disc area than did MBG patients in 3 of the 4 criteria. Signal strength affected the diagnostic performance of cRNFL thickness measurement (P = 0.043), whereas that of macular thickness was not affected by any covariate analyzed. Overall, cRNFL thickness measurements were generally superior to those of macular thickness when used to diagnose glaucoma. Macular thickness parameters were of greater value in eyes with larger optic discs.

Optic Disc Dimensions and Cup-Disc Ratios among Healthy South Indians: The Chennai Glaucoma Study

Purpose: To present optic disc and cup dimensions, cup-disc ratios (CDRs) and asymmetry among healthy South Indians, and their associations with ocular and systemic variables.Methods: A total of 623 healthy phakic participants of the Chennai Glaucoma Study underwent complete eye examinations including optic disc stereo-photography. Planimetry was performed under stereo-viewing conditions. The morphological type of cupping (no cups, steep cups, partly sloping and fully sloping cups) was identified based on a modification of the classification by Jonas et al. The associations of planimetric measures (optic disc area, cup area and vertical cup-disc ratio [VCDR]) with age, gender, height, intraocular pressure, refraction, astigmatism, axial length and corneal thickness as explanatory variables were examined. The associations of asymmetries in the above planimetric measures with age, gender and asymmetries of the above explanatory variables were examined.Results: Mean optic disc and cup areas were 2.82 ± 0.52 mm2 and 0.53 ± 0.39 mm2. Mean CDR was 0.36 ± 0.18. Men had larger discs (P = 0.03). Cup area and VCDR revealed significant associations with disc area (P <0.0001) and type of cupping (P < 0.0001). Mean disc and cup area asymmetries were 0.19 ± 0.16 mm2 and 0.15 ± 0.15 mm2. Mean VCDR asymmetry was 0.07 ± 0.08 mm2. Cup area and VCDR asymmetries showed significant associations with disc area asymmetry (P < 0.0001, both) and asymmetry in the presence or absence of physiological cupping, i.e. subjects with physiological cupping in one eye and no cupping in the other (P < 0.0001, both).Conclusions: We present normative optic disc, cup and VCDR measures and asymmetries among healthy South Indians. We demonstrated the dependence of VCDR on the morphological type of cupping.

Variation in Optic Nerve and Macular Structure with Age and Race with Spectral-Domain Optical Coherence Tomography

To evaluate the effects of age and race on optic disc, retinal nerve fiber layer (RNFL), and macular measurements with spectral-domain optical coherence tomography (SD OCT). Cross-sectional observational study. Three hundred fifty adult subjects without ocular disease. Data from SD OCT imaging of the optic nerve head, peripapillary RNFL, and macula of 632 eyes from 350 subjects without ocular disease were imaged with SD OCT. Multivariate models were used to determine the effect of age and race on quantitative measurements of optic disc, RNFL, and macula. Optic nerve, RNFL, and macular measurements with SD OCT across racial strata and age. For optic nerve parameters, participants of European descent had significantly smaller optic disc area than other groups (P<0.0001), and Indian participants had significantly smaller rim area than other groups (P<0.0001). Indian and Hispanic participants had thicker global RNFL measurements than other groups (P<0.0001). Participants of African descent were associated with thinner inner retinal thickness in the macula (P<0.0001). Age was associated with several parameters, with rim area reducing by 0.005 mm(2)/year, RNFL thickness reducing by 0.18 μm/year, and inner retinal thickness reducing by 0.1 μm/year (P<0.0001 for all age associations). Optic nerve, RNFL, and macular measurements with SD OCT all varied across racial groups and with age. These differences are important in defining the range of normal variation in differing populations and should be considered in the use of these instruments in the detection of optic nerve and macular disease across these population groups. Proprietary or commercial disclosure may be found after the references.

A formula to predict spectral‐domain OCT retinal nerve fiber layer measurements based on time‐domain OCT measurements

AbstractPurpose To establish and validate a formula to predict spectral‐domain optical coherence tomography (SD‐OCT) retinal nerve fiber layer (RNFL) thickness from time‐domain (TD)‐OCT RNFL measurements and other factors.Methods From healthy participants and patients with glaucoma, SD‐OCT and TD‐OCT scans were obtained on the same day. Univariate and multivariate linear regression relationships were analyzed to convert Stratus TD‐OCT measurements to Cirrus SD‐OCT measurements. Other baseline characteristics included were age, gender, intraocular pressure, central corneal thickness, spherical equivalent, anterior chamber depth, optic disc area, visual field mean deviation, and pattern standard deviation. The formula was generated using a training set of 220 patients and then evaluated on a validation dataset of 105 patients.Results Univariate analysis determined that TD‐OCT RNFL thickness, age, optic disc area, visual field mean deviation, and pattern standard deviation were significantly associated with SD‐OCT RNFL thickness. Multivariate stepwise regression analysis using available variables yielded the following equation: SD‐OCT RNFL = 0.746 × TD‐OCT RNFL + 17.104 (R2 = 0.879). In the validation sample, the multiple regression model explained 85.6% of the variance in the SD‐OCT RNFL thickness.Conclusion This formula based on TD‐OCT RNFL thickness may be useful in predicting SD‐OCT RNFL thickness. Other factors associated with SD‐OCT RNFL thickness, such as age, disc area, and mean deviation, did not contribute to the accuracy of the final equation.

The Effects of Race, Optic Disc Area, Age, and Disease Severity on the Diagnostic Performance of Spectral-Domain Optical Coherence Tomography

To evaluate the effect of race (African or European descent), age, disc area, and severity of disease on the diagnostic ability of spectral-domain optical coherence tomography (SDOCT) imaging of the optic nerve, macula, and retinal nerve fiber layer (RNFL) in the detection of glaucomatous injury. In this cross-sectional observational study, data from SDOCT images of 312 eyes of 167 subjects without ocular disease and 233 eyes of 163 patients with open-angle glaucoma. A receiver operating characteristic (ROC) regression modeling technique was used to evaluate the influence of race on the diagnostic accuracy of the ONH, RNFL, and macular parameters in SDOCT in glaucoma, while adjusting and evaluating the possible confounding effects of age, disease severity, and size of the optic disc. The optimal performing measurements of the RNFL and macula were more effective than optic nerve (aROC(RNFL) = 0.87, aROC(inner macula) = 0.88, and aROC(rim area) = 0.81) for the overall group. No variation was noted in the diagnostic performance of SDOCT between racial groups nor was there any association of race with differences in disc area for structural parameters of the optic nerve, RNFL, and macula. Advanced disease severity was associated with increased diagnostic accuracy, with improved performance in eyes with more severe visual field loss. The diagnostic ability of ONH, RNFL, and macular measurements in the detection of glaucoma was similar across racial groups, and disc area had a minimal effect on the overall diagnostic efficacy of SDOCT. No significant differences were seen in the diagnostic performance of the SDOCT between these groups when generalized or race-specific normative data were used.

Ophthalmic Phenotypes and the Representativeness of Twin Data for the General Population

To compare the distributional parameters for a series of ocular biometric traits between twins and their singleton siblings, to evaluate the generalizability of twin data, as used in heritability analyses to the general population. A series of birth, anthropometric, and 13 ocular biometric traits were selected for analysis: interpupillary distance (IPD), visual acuity (logMAR), spherical equivalent refractive error, corneal curvature, axial length, anterior chamber depth (ACD), central corneal thickness (CCT), intraocular pressure (IOP), optic disc, cup and rim areas, and measures of retinal vessel caliber; central retinal arteriolar equivalent (CRAE), and central retinal venular equivalent (CRVE). Structural equation modeling was used to test the assumption that the means and variances for each trait did not differ between twins and their siblings. Significant differences in log-likelihood for birth weight and gestational age were observed between twins and siblings, with the latter being both heavier and closer to full-term at birth. Siblings were also found to have larger IPD and axial length, and better visual acuity compared with their twin counterparts. Refractive error, corneal curvature, ACD, CCT, optic disc parameters, and retinal vascular calibers did not differ significantly between the two groups. Twins are representative of the general population for some but not all measures of ocular biometry. Consequently, care should be taken when extrapolating twin data for these traits in heritability and other genetic studies. Birth weight differences between twins and siblings do not appear to account for the differences in ocular biometry observed in this study.

Shrinkage of the Scleral Canal During Cupping Reversal in Children

The mechanism of cupping reversal seen after lowering intraocular pressure (IOP) in pediatric glaucoma is unknown. Theories include forward movement of the lamina cribrosa or shrinkage of a stretched scleral canal. Our study aimed to quantify changes in optic disc size occurring in children who had undergone glaucoma surgery. Retrospective, single-center, observational case series. Children undergoing incisional surgery for pediatric glaucoma at the University of California, Davis. The electronic charts of all patients with pediatric glaucoma were reviewed for the presence of RetCam digital optic nerve photographs (Clarity Medical Systems, Pleasanton, CA). Cases in which the photographs (baseline and follow-up after surgical intervention) were of sufficient quality were analyzed. The optic disc margin was outlined manually using ImageJ software. Inter-session changes in magnification were accounted for by drawing a control polygon joining 4 or 5 fixed landmarks (e.g., vessel crossings) to include a second larger area containing the optic nerve. The optic disc area (in pixels adjusted with the control polygon) was compared between baseline and follow-up images. Change in disc area between baseline and follow-up after surgery. We identified 29 eyes for which baseline and follow-up images were available for analysis. Fifteen eyes of 9 children showed clinically obvious cupping reversal. Fourteen eyes of 12 children showed no cupping reversal. Disc area decreased by 6.8% (95% confidence interval [CI], -10.0 to -3.3) in the obvious reversal group and increased by 4.3% (95% CI, +1.0 to +7.6) in the no reversal group after surgery (P < 0.0001; Student t test). Percent change in disc area is correlated to percent change in IOP (r=0.540; P=0.0025) and axial length (r=0.534; P=0.0028). When cupping reversal is clinically apparent after successful IOP-lowering surgery for congenital glaucoma, the scleral canal shrinks in area. In contrast, when cupping reversal is not observed, the scleral ring continues to enlarge, indicating ongoing stress on the optic nerve. Clinically obvious cupping reversal is less frequently observed in adults after surgery, which may reflect a lower elasticity of the scleral ring in adults compared with children. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

CHANGES IN AREAS OF CAPILLARY NONPERFUSION AFTER INTRAVITREAL INJECTION OF BEVACIZUMAB IN EYES WITH BRANCH RETINAL VEIN OCCLUSION

: To study the effect of an intravitreal bevacizumab (IVB) on the retinal ischemia in eyes with a branch retinal vein occlusion. : Fluorescein angiography was performed before and 1 month after the IVB (1.25 mg/0.05 mL) in 58 consecutive eyes of 58 patients with macular edema secondary to a branch retinal vein occlusion. The area of capillary nonperfusion was measured on an early-phase fluorescein angiography image by an area measurement program, and the area was expressed relative to the optic disk area (DA). A blockage of the fluorescence by the retinal hemorrhage was distinguished from nonperfusion by comparisons with retinal photographs. : Thirty-seven of 58 eyes did not have any capillary nonperfusion before the IVB, and capillary nonperfusion developed in 3 of these 37 eyes 1 month after the IVB. The area of nonperfusion in these 3 eyes was 0.13, 0.47, and 0.60 DA. Twenty-one of the 58 eyes had capillary nonperfusion before the IVB, and the mean (±SD) area of nonperfusion was 3.45 ± 4.66 DA before the IVB and 3.45 ± 5.19 DA 1 month after the IVB. This change was not significant (P = 0.36). An increase in the area of capillary nonperfusion of >1.0 DA after the IVB was seen in only 1 of all 58 eyes. : These results suggest that the incidence of a significant increase in the area of capillary nonperfusion (>1 DA) during the 1 month after the IVB is very low in eyes with branch retinal vein occlusion.

Determinants of Perimacular Inner Retinal Layer Thickness in Normal Eyes Measured by Fourier-Domain Optical Coherence Tomography

To determine the effects of age, sex, spherical equivalent, axial length, anterior chamber depth, optic disc area, and central corneal thickness on perimacular inner retinal layer thickness in the normal human eye as measured by Fourier-domain optical coherence tomography (FD-OCT). In this cross-sectional observational study, 182 Korean healthy subjects aged from 22 to 84 years were included. To obtain the inner retinal layer thickness, perimacular ganglion cell complex thickness, which extends from the internal limiting membrane to the inner nuclear layer, was measured by FD-OCT on one randomly selected eye of each subject. Linear regression analyses of the effects of demographic and clinical variables, including age, sex, spherical equivalent, axial length, anterior chamber depth, optic disc area, and central corneal thickness, on perimacular inner retinal layer thickness were performed. The mean inner retinal layer thickness for the entire population was 93.87 μm. Thinner inner retinal layer measurements were associated with older age (P = 0.010) and greater axial length (P = 0.021). Mean inner retinal layer thickness decreased by approximately 1.59 μm for every decade of age and by approximately 1.56 μm for every 1-mm greater axial length. There was no relationship between inner retinal layer thickness and sex, anterior chamber depth, optic disc area, or central corneal thickness. Inner retinal layer thickness, as measured by FD-OCT, varies significantly with age and axial length. The effect is small but clinically relevant in the interpretation of inner retinal layer thickness measurements.

Influence of Refractive Error on Optic Disc Topographic Parameters: The Singapore Malay Eye Study

To examine the relationship between refractive error and optic disc topographic parameters and retinal nerve fiber layer (RNFL) thickness. Population-based cross-sectional study. All 3,280 (78.7% response rate) persons of Asian Malay ethnicity 40 to 80 years of age underwent a standardized interview, ocular examinations, and optic disc imaging with the Heidelberg Retina Tomography II (HRT; Heidelberg Engineering). Associations between spherical equivalent (SE) and HRT parameters were evaluated by partial correlation analysis. There were 2,457 (74.9%) right eyes with good-quality HRT images for analyses. When compared with emmetropic eyes, highly myopic eyes (SE < -6.0 diopters) had greater disc area, rim area, rim volume, whereas hyperopic eyes (SE > 0.5 diopters) had significantly smaller disc area, rim area, and cross-sectional RNFL area (all P < .005). In partial correlation after adjustment for age, sex, body mass index, intraocular pressure, and optic disc area, increase of SE (toward hyperopia) was related significantly with greater cup area (partial correlation coefficient, r = 0.058; P = .004) and cup-to-disc area ratio (r = 0.058; P = .004) and with smaller optic disc area (r = -0.058; P = .004), rim area (r = 0.058; P = .004), and rim volume (r = -0.091; P < .001). This population-based study shows that refractive error is significantly (but weakly) associated with HRT parameters of disc area, cup area, rim area, cup-to-disc area ratio, and rim volume. The clinical significance of these associations need to be determined in further studies.

Optic disc area and correlation with central corneal thickness, corneal hysteresis and ocular pulse amplitude in glaucoma patients and controls: comment

Optic disc area and correlation with central corneal thickness, corneal hysteresis and ocular pulse amplitude in glaucoma patients and controls: comment

Optic disc area and correlation with central corneal thickness, corneal hysteresis and ocular pulse amplitude in glaucoma patients and controls: response

Optic disc area and correlation with central corneal thickness, corneal hysteresis and ocular pulse amplitude in glaucoma patients and controls: response

Genetic Variants Associated with Optic Nerve Vertical Cup-to-Disc Ratio Are Risk Factors for Primary Open Angle Glaucoma in a US Caucasian Population

Genetically complex disorders, such as primary open angle glaucoma (POAG), may include highly heritable quantitative traits as part of the overall phenotype, and mapping genes influencing the related quantitative traits may effectively identify genetic risk factors predisposing to the complex disease. Recent studies have identified SNPs associated with optic nerve area and vertical cup-to-disc ratio (VCDR). The purpose of this study was to evaluate the association between these SNPs and POAG in a US Caucasian case-control sample. Five SNPs previously associated with optic disc area, or VCDR, were genotyped in 539 POAG cases and 336 controls. Genotype data were analyzed for single SNP associations and SNP interactions with VCDR and POAG. SNPs associated with VCDR rs1063192 (CDKN2B) and rs10483727 (SIX1/SIX6) were also associated with POAG (P = 0.0006 and P = 0.0043 for rs1063192 and rs10483727, respectively). rs1063192, associated with smaller VCDR, had a protective effect (odds ratio [OR] = 0.73; 95% confidence interval [CI], 0.58-0.90), whereas rs10483727, associated with larger VCDR, increased POAG risk (OR = 1.33; 95% CI, 1.08-1.65). POAG risk associated with increased VCDR was significantly influenced by the C allele of rs1900004 (ATOH7), associated with increased optic nerve area (P-interaction = 0.025; OR = 1.89; 95% CI, 1.22-2.94). Genetic variants influencing VCDR are associated with POAG in a US Caucasian population. Variants associated with optic nerve area are not independently associated with disease but can influence the effects of VCDR variants suggesting that increased optic disc area can significantly contribute to POAG risk when coupled with risk factors controlling VCDR.

Common genetic variants associated with open-angle glaucoma

Open-angle glaucoma (glaucoma) is a major eye disorder characterized by optic disc pathology. Recent genome-wide association studies identified new loci associated with clinically relevant optic disc parameters, such as the optic disc area and vertical cup-disc ratio (VCDR). We examined to what extent these loci are involved in glaucoma. The loci studied include ATOH7, CDC7/TGFBR3 and SALL1 for optic disc area, and CDKN2B, SIX1, SCYL1/LTBP3, CHEK2, ATOH7 and DCLK1 for VCDR. We performed a meta-analysis using data from six independent studies including: the Rotterdam Study (n= 5736), Genetic Research in Isolated Populations combined with Erasmus Rucphen Family study (n= 1750), Amsterdam Glaucoma Study (n= 296) and cohorts from Erlangen and Tübingen (n= 1363), Southampton (n= 702) and deCODE (n= 36 151) resulting in a total of 3161 glaucoma cases and 42 837 controls. Of the eight loci, we found significant evidence (P= 1.41 × 10(-8)) for the association of CDKN2B with glaucoma [odds ratio (OR) for those homozygous for the risk allele: 0.76; 95% confidence interval (CI): 0.70-0.84], for the role of ATOH7 (OR: 1.28; 95% CI: 1.12-1.47) and for SIX1 (OR: 1.20; 95% CI: 1.10-1.31) when adjusting for the number of tested loci. Furthermore, there was a borderline significant association of CDC7/TGFBR3 and SALL1 (both P= 0.04) with glaucoma. In conclusion, we found consistent evidence for three common variants (CDKN2B, ATOH7 and SIX1) significantly associated with glaucoma. These findings may shed new light on the pathophysiological protein pathways leading to glaucoma, and point to pathways involved in the growth and development of the optic nerve.

Characteristics and appearance of the normal optic nerve head in 6-year-old children

AimTo document planimetric measures of normal optic nerve head parameters in 6-year-old children and to report prevalence and associations of common optic nerve signs.MethodsThe Sydney Childhood Eye Study examined 1765...

Comparison of Automated Analysis of Cirrus HD OCT Spectral-Domain Optical Coherence Tomography with Stereo Photographs of the Optic Disc

To evaluate a new automated analysis of optic disc images obtained by spectral-domain optical coherence tomography (SD OCT). Areas of the optic disc, cup, and neural rim in SD OCT images were compared with these areas from stereoscopic photographs to represent the current traditional optic nerve evaluation. The repeatability of measurements by each method was determined and compared. Evaluation of diagnostic technology. One hundred nineteen healthy eyes, 23 eyes with glaucoma, and 7 glaucoma suspect eyes. Optic disc and cup margins were traced from stereoscopic photographs by 3 individuals independently. Optic disc margins and rim widths were determined automatically in SD OCT. A subset of photographs was examined and traced a second time, and duplicate SD OCT images also were analyzed. Agreement among photograph readers, between duplicate readings, and between SD OCT and photographs were quantified by the intraclass correlation coefficient (ICC), by the root mean square, and by the standard deviation of the differences. Optic disc areas tended to be slightly larger when judged in photographs than by SD OCT, whereas cup areas were similar. Cup and optic disc areas showed good correlation (0.8) between the average photographic reading and SD OCT, but only fair correlation of rim areas (0.4). The SD OCT was highly reproducible (ICC, 0.96-0.99). Each reader also was consistent with himself on duplicate readings of 21 photographs (ICC, 0.80-0.88 for rim area and 0.95-0.98 for all other measurements), but reproducibility was not as good as SD OCT. Measurements derived from SD OCT did not differ from photographic readings more than the readings of photographs by different readers differed from each other. Designation of the cup and optic disc boundaries by an automated analysis of SD OCT was within the range of variable designations by different readers from color stereoscopic photographs, but use of different landmarks typically made the designation of the optic disc size somewhat smaller in the automated analysis. There was better repeatability among measurements from SD OCT than from among readers of photographs. The repeatability of automated measurement of SD OCT images is promising for use both in diagnosis and in monitoring of progression.

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Predictors of Normal Optic Nerve Head, Retinal Nerve Fiber Layer, and Macular Parameters Measured by Spectral Domain Optical Coherence Tomography

To evaluate the effects of signal strength, age, sex, optic disc size, and axial length on the normal optic nerve head (ONH), retinal nerve fiber layer (RNFL), and macular measurements with spectral domain optical coherence tomography (SD-OCT). In an observational, cross-sectional study, 119 eyes of 60 normal subjects of Indian origin underwent ONH, RNFL, and macular imaging with SD-OCT during the same visit. Linear mixed-modeling methods were used to evaluate the effects of signal strength, age, sex, optic disc area, and axial length on ONH, RNFL, and macular measurements. ONH rim measurements increased and cup measurements decreased with increasing signal strengths. For a 10-unit increase in signal strength, total rim area increased by a mean of 0.1 mm(2). ONH measurements also increased with increasing optic disc size. Rim measurements decreased and cup measurements increased with increasing axial length. None of the predictors influenced RNFL measurements. Macular inner retinal thickness decreased by a mean of 1.7 μm and macular full retinal thickness decreased by an average of 3.4 μm for every decade's increase in age. Sex did not influence any of the measurements. Signal strength, optic disc size, and axial length had a significant effect on ONH measurements, whereas age had a significant effect on macular measurements. None of the predictors evaluated influenced the RNFL measurements. These predictors should be considered when evaluating change in the structural measurements in glaucoma over time.