Optic Disc Size Research Articles

Blood vessel inpainting based technique for efficient localization and segmentation of optic disc in digital fundus images

Abstract The Optic disc (OD) nerve head region in general and OD center coordinates in particular form basis for study and analysis of various eye pathologies. The shape, contour and size of OD is vital in classification and grading of retinal diseases like glaucoma. There is a need to develop fast and efficient algorithms for large scale retinal disease screening. With this in mind, this paper present a novel framework for fast and fully automatic detection of OD and its accurate segmentation in digital fundus images. The methodology involves optic disc center localization followed by removal of vascular structure by accurate inpainting of blood vessels in the optic disc region. An adaptive threshold based Region Growing technique is then employed for reliable segmentation of fundus images. The proposed technique achieved significant results when tested on standard test databases like MESSIDOR and DRIVE with average overlapping ratio of 89% and 87%, respectively. Validation experiments were done on a labeled dataset containing healthy and pathological images obtained from a local eye hospital achieving an appreciable 91% average OD segmentation accuracy.

Glaucomatous-Type Optic Discs in High Myopia.

PurposeTo assess the prevalence of glaucoma in patients with high myopia defined as myopic refractive error of >-8 diopters or axial length ≥26.5 mm.MethodsThe hospital-based observational study included 172 patients (336 eyes) with a mean age of 61.9±12.3 years and mean axial length of 30.1±2.3 mm (range: 24.7–39.1mm). Glaucomatous-type optic discs were defined by glaucomatous optic disc appearance. Glaucoma was defined by glaucomatous optic disc appearance and glaucomatous Goldmann visual field defects not corresponding with myopic macular changes.ResultsLarger disc area (mean: 3.18±1.94 mm2) was associated with longer axial length (P<0.001; standardized correlation coefficient: 0.45). Glaucoma was detected in 94 (28%; 95% Confidence intervals: 23%, 33%) eyes. In multivariate analysis, glaucoma prevalence was 3.2 times higher (P<0.001) in megalodiscs (>3.79 mm2) than in normal-sized discs or small discs (<1.51 mm2) after adjusting for older age. Axial length was not significantly (P = 0.38) associated with glaucoma prevalence in that model. Glaucoma prevalence increased by a factor of 1.39 for each increase in optic disc area by one mm2. Again, axial length was not significantly (P = 0.38) associated with glaucoma prevalence when added to this multivariate model.ConclusionWithin highly myopic individuals, glaucoma prevalence increased with larger optic disc size beyond a disc area of 3.8 mm2. Highly myopic megalodiscs as compared to normal sized discs or small discs had a 3.2 times higher risk for glaucomatous optic nerve neuropathy. The increased glaucoma prevalence in axial high myopia was primarily associated with axial myopia associated disc enlargement and not with axial elongation itself.

Automatic Localization of the Optic Disc Center in Retinal Images based on Angle Detection in Curvature Scale Space

Digital images of the retina is widely used for screening of patients suffering from sight threatening diseases such as Diabetic retinopathy and Glaucoma. The localization of the Optic Disc (OD) center is the first and necessary step identification and segmentation of anatomical structures and in pathological retinal images. From the center of the optic disc spreads the major blood vessels of the retina. Therefore, by considering the high number of vessels and the high number of the angles resulted from the vessels crossing, the authors propose a new method based on the number of angles in the vicinity of optic disc for localization of the center of optic disc. The first step is pre-processing of retinal image for separate the fundus from its background and increase the contrast between contours. In the second step, the authors use the Curvature Scale Space (CSS) for angle detection. In the next step, they move a window about the size of optic disc to count the number of corners. In the final step, they use the center of windows which has the most number of corners for localizing the optic disc center. The proposed method is evaluated on DRIVE, CHASE_DB1 and STARE databases and the success rate is 100, 100 and 96.3%, respectively.

Optic Disk Size Assessment Techniques: Photo Essay

Measuring optic disc size is an essential part of the optic nerve head for evaluation for glaucoma. Large discs that appearing to have large cups may in fact be physiologic because of normal neuroretinal rim area. Small discs may appear to have a normal cup to disc ratio, but have decreased neuroretinal rim area in association with glaucoma. We illustrate relevance of these points with respect to glaucoma diagnosis in two case examples. We then present clinically relevant techniques to assess disc size including direct ophthalmoscopy, slit lamp biomicroscopy, disc macula: disc diameter ratio, planimetric assessment of fundus photographs, and imaging modalities such as OCT as well as HRT.

Therapeutic endorsement enhances compliance with national glaucoma guidelines in Australian and New Zealand optometrists.

Previous studies confirmed that optometrists have access to and confidence in applying clinical tests recommended for glaucoma assessment. Less is known about factors best predicting compliance with national clinical guidelines and thus by inference, the provision of suitable care by primary care ophthalmic practitioners. We utilised the unique two-tiered profession (therapeutic and non-therapeutic scope of practice) in Australia and New Zealand to assess the prospective adherence to glaucoma guidelines dependent on the clinician's background. Australian and New Zealand optometrists were surveyed on ophthalmic techniques for glaucoma assessment, criteria for the evaluation of the optic nerve head, glaucoma risk categories and review times while also recording background, training, and experience. Parameters identifying progression/conversion and patients' risk levels were analysed comparatively to ophthalmologists' opinions. Linear regression analysis identified variables significantly improving the likelihood of concordance with guidelines. Reported application of techniques complied well with glaucoma guidelines although gonioscopy and pachymetry, pupil dilation for optic nerve head examination, and acquisition of permanent records were less frequently employed. The main predictors for entry-level diagnostic standards were therapeutic endorsement together with the associated knowledge of relevant guidance and procedural confidence. Other findings suggested a potential underestimation in the value of optic disc size and intraocular pressure for the prediction of glaucoma risk, while optometrists more frequently relied on the outcomes of non-standardised automated perimetry and auxiliary imaging. Optometrists in Australia and New Zealand may not always exercise optimal clinical acumen regarding techniques/criteria for glaucoma diagnosis. Therapeutic endorsement was gradually adopted in different jurisdictions in various forms since 1999 and is mandatory for registration since late 2014. The result of the two-tiered optometric cohorts suggest that inclusion of therapeutic training as part of the core training is likely a key factor to enhanced compliance with glaucoma guidelines. Improved adherence to the current clinical standards should positively impact on the facilitation of appropriate glaucoma diagnosis and management. Obligatory knowledge and possibly accreditation of available guidelines might ensure a uniform standard in glaucoma testing protocols in concordance with compulsory entry-level skills.

Optic Nerve Head Changes after Short-Term Intraocular Pressure Elevation in Acute Primary Angle-Closure Suspects

To investigate changes in the optic nerve head morphology after acute intraocular pressure (IOP) elevation during a dark room prone provocative test (DRPPT). Prospective cohort study. Acute primary angle-closure (APAC) suspects underwent DRPPT. Study participants stayed in a dark room for 2 hours with the forehead placed on a desk. At baseline and within 5 minutes after DRPPT, tonometry and enhanced depth imaging by spectral-domain optical coherence tomography (SD OCT) were performed. Changes in 3-dimensional optic nerve head topography. The study included 114 eyes of 65 participants with a mean age of 58.3±8.7 years and a mean IOP elevation of 10.1±10.9 mmHg during DRPPT. When all eyes were included, the mean value of most optic disc parameters did not change significantly, except for a decrease in the temporal minimal rim width (P = 0.005). By including only eyes with an IOP increase greater than 15 mmHg, the mean value of cup width (P = 0.001) and cup depth (P = 0.002) increased, whereas the lamina cribrosa (LC) thickness (P = 0.035), temporal minimal rim width (P = 0.001), and nasal minimal rim width (P < 0.001) decreased. The LC depth and Bruch's membrane opening (BMO) did not differ between the baseline and the end of DRPPT. An IOP increase was significantly associated with widening (P < 0.001; r = 0.46) and deepening (P < 0.001; r = 0.52) of the optic cup, thinning of the LC (P = 0.003; r = -0.35), temporal minimal rim width (P < 0.001; r = -0.34), and nasal minimal rim width (P < 0.001; r = -0.35). Angle-closure suspect eyes showed a widening and deepening of the optic cup, decrease in neuroretinal rim width, and thinning of the LC after a darkness-induced IOP increase of >15 mmHg. The diameter of the BMO and position of the anterior LC surface remained unchanged. This suggests that a short-term IOP increase leads to a condensation of neuroretinal rim, prelaminar tissue, and LC, without major changes in the optic disc size and position of the anterior LC surface.

A hierarchical framework for estimating neuroretinal rim area using 3D spectral domain optical coherence tomography (SD-OCT) optic nerve head (ONH) images of healthy and glaucoma eyes.

Glaucoma is a chronic neurodegenerative disease characterized by loss of retinal ganglion cells, resulting in distinctive changes in the optic nerve head (ONH) and retinal nerve fiber layer (RNFL). Important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, a crucial step in diagnosing and monitoring glaucoma. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new approach for locating the Bruch's membrane opening BMO and then estimating the optic disc size and rim area of 3D Spectralis SD-OCT images. To deal with the overlapping of the Bruch's membrane BM layer and the border tissue of Elschnig due to the poor image resolution, we propose the use of image deconvolution approach to separate these layers. To estimate the optic disc size and rim area, we propose the use of a new regression method based on the artificial neural network principal component analysis (ANN-PCA), which allows us to model irregularity in the BMO estimation due to scan shifts and/or poor image quality. The diagnostic accuracy of rim area, and rim to disc area ratio is compared to the diagnostic accuracy of global RNFL thickness measurements provided by two commercially available SD-OCT devices using receiver operating characteristic curve analyses.

The ISNT rule in glaucoma: revisiting with spectral domain optical coherence tomography.

To evaluate the ability of the neuroretinal rim (NRR) rules determined using spectral domain optical coherence tomography (SDOCT) in diagnosing glaucoma and to study the effect of optic disc size and disease severity on the diagnostic ability of these rules. In a cross-sectional study, 125 eyes of 96 glaucoma patients and 96 eyes of 72 control subjects underwent optic nerve head (ONH) imaging with SDOCT. Inferior (I), superior (S), nasal (N) and temporal (T) NRR areas were automatically determined by the sdoct software. Diagnostic abilities of ISNT (I > S > N > T), IT (I > T) and ST (S > T) rules in glaucoma were evaluated using sensitivity, specificity and likelihood ratios (LR). Effect of optic disc size and disease severity [based on mean deviation (MD) on visual fields] on the diagnostic ability of the NRR rules was evaluated using regression models. Sensitivities of ISNT, IT and ST rules were 80.8%, 60.0% and 29.6%, respectively, and the specificities were 32.3%, 84.4% and 93.8%, respectively. Positive LRs of ISNT, IT and ST rules were 1.19, 3.84 and 4.74, respectively, and negative LRs were 0.60, 0.47 and 0.75, respectively. Sensitivities of ISNT (coefficient: -1.06, p = 0.02) and IT (-0.71, 0.05) rules decreased with increasing disc size. Positive LR of IT rule increased significantly (-0.01, 0.04) with decreasing MD, and negative LR of IT rule decreased (got better) significantly (0.26, 0.05) with decreasing disc size. Neuroretinal rim rules, as determined by SDOCT, do not allow robust differentiation of glaucomatous from non-glaucomatous discs.

Analysis of ocular changes in children craniopharyngioma

To analyze the characteristics of ocular changes in children craniopharyngioma. Retrospective case series study. The clinical data of 34 eyes from 17 patients with children craniopharyngioma treated at the affiliated Beijing Tiantan Hospital, Capital Medical University from September 2011 to May 2012 were collected. Records of preoperative clinical examinations including best corrected visual acuity (BCVA), visual field test, optic disc findings, size and location of the tumor were analyzed. The age of the patients was from 5 to 14 years old [mean (10.29 ± 3.22) years] with the male/female ratio of 1.83: 1. The most affected age group was 8 to 12 years old. Deficits in BCVA occurred in 79.41% (27/34). Abnormal optic disc findings occurred in 44.12% which included optic disk edema 5.9% (2/34), atrophic changes of the optic nerve 32.35% (11/34) and pale optic disc 5.9% (2/34). Various visual field defects were 76.47% (26/34). Declines of visual acuities and defects of visual fields were more severe than optic disc damages in children patients with craniopharyngioma.

An investigation of lateral geniculate nucleus volume in patients with primary open-angle glaucoma using 7 tesla magnetic resonance imaging.

To investigate lateral geniculate nucleus (LGN) volume of primary open-angle glaucoma (POAG) patients compared with age- and sex-matched controls using ultra-high field 7.0-T magnetic resonance imaging (MRI). The study included 18 patients with POAG and 18 age- and sex-matched healthy volunteers. All subjects underwent imaging on a high-resolution 7.0-T MRI system. Bilateral LGNs were identified and manually delineated, and LGN volumes were compared. Peripapillary retinal nerve fiber layer (pRNFL) thickness, optic nerve head parameters (including optic disc size, rim area, and cup-to-disc ratio), and combined thickness of the ganglion cell layer and inner plexus layer (GC-IPL) were measured by Cirrus high-definition optical coherence tomography (OCT). Correlations between OCT parameters and LGN volume were investigated. Mean LGN volumes were significantly smaller in the POAG group than in the control group (right, glaucoma 83.97 mm(3) [SD ± 26.65] versus control 106.12 mm(3) [SD ± 24.32]; left, glaucoma 65.12 mm(3) [SD ± 29.41] versus control 92.70 mm(3) [SD ± 24.42], both P < 0.05). In the POAG group, average GC-IPL thickness was correlated with contralateral LGN volume (right LGN: r = 0.605, P = 0.008; left LGN: r = 0.471, P = 0.049). The correlation for right LGN volume remained significant after correction for multiple comparisons. However, there was no correlation between LGN volume and average pRNFL thickness or optic disc parameters in the POAG group. On high-resolution 7.0-T MRI, LGN volumes in POAG patients are significantly smaller than those of healthy subjects. Furthermore, in patients, LGN volume was found to be significantly correlated with GC-IPL thickness of the contralateral eye.

Absence of age-related optic disk changes in young children with optic nerve hypoplasia

To determine whether the ratio of optic disk diameter to disk-to-macula distance (DD/DM) in children with optic nerve hypoplasia (ONH) changes over time. Fifteen subjects (29 eyes) enrolled in a prospective registry study on ONH had fundus photography performed under the age of 24 months and again at 60 months. Using the ratio of the DD/DM method, the relative size of the optic disk was assessed twice for each photo by one masked expert examiner to determine whether any change in relative disk size occurred over time. There was no change in relative optic disk size between initial and final fundus photographs. The average (± SD) age at the time of initial and final fundus photography was, respectively, 11.6 ± 5.2 months and 60.6 ± 1.3 months. Strong concordance was noted between the average DD/DM of the initial and the final photographs (ρ=0.939; 95% CI: 0.893, 0.981). There was negligible difference between the individual time point measurements (-0.011 ± 0.03) (95% LOA: -0.07, 0.04). There were no clinically significant changes in relative optic disk size over time in children with ONH; thus, DD/DM measurements need not be adjusted by age beyond 1 year in children with this disorder.

Clinical features and glaucoma according to optic disc size in a South Korean population: the Namil study

To assess the proportion of glaucomatous eyes based on the association between optic disc (OD) size and its clinical determinants in the resident population of Namil-myon, Central South Korea. Of the 1,532 participants in the Namil study, we included 1,410 Koreans (2,734 eyes) with legible fundus photographs in this study. Following the estimation of OD size on the photographs using Image J software, we corrected for image magnification. Associations between the clinical features, such as age, sex, axial length (AL), spherical equivalent (SE), and central corneal thickness, and the estimated OD size were assessed for individual eyes. After adjusting for the influencing factors, the proportion of glaucoma was compared among three categories of measured OD size (small, medium, and large OD groups). After adjusting for the potential confounders using a linear mixed model, age, sex, AL, and SE were correlated with the OD size estimates (P = 0.003, P = 0.029, P < 0.001, and P < 0.001, respectively). The percentage of glaucomatous eyes was 3.77 % in the small disc group, which was higher than in the other groups (P = 0.054). In particular, normal tension glaucoma (NTG) was statistically significantly more frequent in this group (odds ratio = 1.86, P = 0.042). These results suggest that clinical features such as age, sex, AL, and SE might need to be considered for an accurate evaluation of the OD. In addition, in individuals with a small OD, the presence of NTG must be carefully investigated in the South Korea population.

Clarifying the role of ATOH7 in glaucoma endophenotypes

Background/aimsThe ATOH7 gene has been previously associated with glaucoma and glaucoma-related traits, such as disc size and cup/disc ratio (CDR). CDR is an important part of the glaucoma phenotype, whereas...

Glaucoma diagnostic value of the total macular thickness and ganglion cell-inner plexiform layer thickness according to optic disc area

AimsThis study examined the diagnostic value of the perimacular ganglion cell-inner plexiform layer (GCIPL) thickness in the detection of glaucoma according to the optic disc area.MethodsThe participants underwent reliable standard...

Depth and area of retinal nerve fiber layer damage and visual field correlation analysis.

PurposeTo evaluate the relationship between the structural damage as assessed by time-domain optical coherence tomography (OCT) and functional changes in glaucoma.MethodsIn total, 190 patients with normal tension glaucoma or primary open angle glaucoma were included in this study. The thickness of retinal nerve fiber layer (RNFL) around the optic disc and the area of RNFL defect were determined using OCT scans. The relationships between the RNFL thickness or area of the defect and visual field (VF) indices were assessed using the Lowess function, regression analysis and partial Spearman correlation. The differences between these associations depending on the stage of VF damage were further analyzed. Age, optic disc size, refraction, central corneal thickness and the presence of systemic disease were corrected for in order to exclude confounding factors.ResultsA logarithmic scale of RNFL thickness showed a negative linear relationship with VF indices. The area of the RNFL defect showed a weak correlation with the pattern of standard deviation, whereas the remnant RNFL thickness was moderately correlated with the pattern of standard deviation (partial Spearman correlation coefficient, 0.39, -0.47, respectively; p < 0.0001). Many outliers were detected in the Lowess-plotted graphs. Multiplication of the area and the inverted RNFL thickness showed a moderately correlated logarithmic relationship with the VF indices (partial Spearman correlation coefficient, 0.46; 95% confidence interval, 0.34 to 0.57; p < 0.0001). In the severe stage of VF damage, correlation between the area of the RNFL defect and mean deviation was significantly greater than in other stages (partial Spearman correlation coefficient, -0.66; p = 0.02).ConclusionsThe thickness of the RNFL had a negative logarithmic correlation with the VF indices and was more relevant to the VF indices than the area of the RNFL defect, as measured by OCT.

About the optic disc size

Aim. To compare the dependence of retinal nerve fibre layer thickness on the optic disc size in confocal scanning laser ophthalmoscopy and optical coherence tomography. Methods. 201 outpatient’s cards with verified diagnosis of glaucoma or with suspicion of glaucoma were retrospectively analyzed. The mean age of the patients was 64 (56; 72) years [Me, (Q1; Q3)]. A group of patients who underwent confocal scanning laser ophthalmoscopy (181 eyes), and a group who underwent optical coherence tomography (183 eyes), were separated. Besides, all the groups were twice divided into 3 subgroups each, by means of cluster analysis and on the basis of size classification: large, medium and small. Results. According to the data of confocal scanning laser ophthalmoscopy, the bigger is the optic disc, the thinner is retinal nerve fibre layer (Rs=-0.22; р=0.001). In optical coherence tomography, different correlation was observed, the bigger is the optic disc, the thicker is the retinal nerve fibre layer (Rs=0.15; р=0.03). Conclusion. The size of the optic disc was related to the retinal nerve fibre layer thickness in both examination modes: there was an inverse relation found in confocal scanning laser ophthalmoscopy - the bigger the optic disc, the thinner is the retinal nerve fibre layer), and there was a direct dependence found in optical coherence tomography (the bigger is the optic disc, the thicker is retinal nerve fibre layer), thus it is important to consider the size of the optic disc while estimating the retinal nerve fibre layer thickness.

Retinal nerve fibre layer thickness measured by Spectralis spectral‐domain optical coherence tomography: The Beijing Eye Study

The aim of this study was to measure retinal nerve fibre layer thickness (RNFLT) and its associated factors in a population-based setting. The population-based Beijing Eye Study 2011 included 3468 individuals. The study participants underwent spectral-domain optical coherence tomography (Spectralis(®) ; Spectralis OCT)-assisted measurement of the RNFLT. For this study, exclusion criteria were glaucoma, pseudoexfoliation, best-corrected visual acuity of >0.5 logMAR, macular diseases, previous ocular surgery and known neurological diseases. The only inclusion criterion was an age of 50+ years. The inclusion criteria were fulfilled by 2548 participants. Mean RNFLT was 102 ± 11 μm. RNFLT was significantly (p < 0.001) thicker in the temporal inferior sector (153 ± 21 μm) than in the temporal superior sector (138 ± 21 μm), nasal inferior sector (118 ± 24 μm), nasal superior sector (106 ± 21 μm), temporal sector (76 ± 13 μm) and nasal sector (73 ± 15 μm). The mean intereye difference in RNFLT was 4.4 ± 6.0 μm. In multivariate analysis, thicker RNFLT was associated with younger age (p < 0.001), female gender (p < 0.001), urban region (p = 0.003), larger optic disc size (p < 0.001), larger neuroretinal rim area (p < 0.001), hyperopic refractive error (p < 0.001), larger beta zone of parapapillary atrophy (p = 0.008) and thicker subfoveal choroidal thickness (p = 0.02). RNFLT decreased by about 0.2 μm (0.2%) per year of life and by 1 μm (1%) per dioptre of myopia. Mean RNFLT (measured by Spectralis(®) OCT; 102 ± 11 μm) was associated with younger age, female gender, urban region of habitation, larger optic disc, larger rim, hyperopic refractive error, larger parapapillary beta zone and thicker subfoveal choroidal thickness. Independent of age and refractive error, the RNFL was thickest temporal inferiorly and thinnest temporally and nasally.

Cognitive function associated with larger optic nerve heads

AbstractPurpose To assess associations between optic nerve head size and parameters of cognitive function in a population‐based study design.Methods The Beijing Eye Study is a population‐based cohort study in Northern China and included 4442 subjects. The study participants underwent a detailed ophthalmologic examination and an interview with questions on the level of education. Using fundus photographs, we measured the size of the optic disc.Results Assessable optic disc photographs were available for 4089 (92.1%) subjects. After adjusting for age, gender, refractive error, and best corrected visual acuity, optic disc size was significantly associated with a higher level of education (P&lt;0.001) and shorter time needed to perform frequency doubling threshold perimetry (P&lt;0.001). In a reverse manner, the level of education was significantly associated with increasing optic disc size (P&lt;0.001) and shorter perimetric test duration (P&lt;0.001) after adjustment for age, gender and best corrected visual acuity.Conclusion In a population‐based study on adult Chinese, optic nerve head size was associated with the highest achieved level of education and time needed to perform a standardized perimetric test. Considering level of education and time needed to perform perimetry as surrogates of cognitive function, optic nerve head size was related to cognitive function.

Effectiveness of the glaucoma screening in employees of the University Hospital St. Luc, UCL, in Brussels

AbstractPurpose To assess the effectiveness of free glaucoma screening for the employees of University Hospital St. Luc, UCL, Brussels, during the World Glaucoma Week 2013.Methods During 1 week, the employees in the university hospital St.Luc, were invited to Glaucoma outpatients' free screening consultation. 320 responded positively. The participants filled before the examination a questionnaire: age, sex, personal ocular trauma or surgery, and familial history was asked. The subjects were examined by an ophthalmologist in training and supervised by an experienced glaucoma consultant if needed (SP). The examination of anterior segment (Van Herick’s, depth, Krukenberg’s spindle, iris transillumination and pseudoexfolliation), the optic disc (size, rim and peripapillary hemorrhages) and the IOP by GAT were performed. Depending of clinical examination, a visual field test was performed. Finally, according to the results, the examiner classified the subjects in ‘Normal’, ‘suspect’ and ‘Glaucoma’ group. A second appointment was scheduled for the patients in the ‘Suspect’ or ‘Glaucoma’ classification.Results From the 640 eyes, there were in total 15% in ‘suspect group’ classified. The aspect of their optic disc and a suspect visual field was the main reason for this classification.5% of the total eyes undergone a preventive iridotomy, none of these patients had experienced any ocular symptoms. 3% of all eyes showed glaucoma with structural and functional glaucomatouse damage.Conclusion Glaucoma is still not widely known. Even for the employees of a large university hospital white easy access to the care, is screening important. The preventive iridotomy was the best result of this WGW screening.

Ethnic Variation in Optic Disc Size by Fundus Photography

Purpose: To compare optic disc size among Caucasian, Chinese, African, Filipino and Hispanic subjects recruited from a university-based general ophthalmology clinic.Methods: In this retrospective cross-sectional study, optic disc size was calculated from fundus photographs. Differences in age, sex and spherical equivalent among the ethnic groups were examined with either Kruskal--Wallis test or Chi-square test. Ethnic differences in optic disc size were evaluated with linear mixed-effects regression models that adjusted for age, sex, spherical equivalent, glaucoma status, lens status and use of both eyes in the same subject.Results: Five hundred and seventy-four eyes of 305 subjects were analyzed. The mean and standard deviation of the optic disc size were 2.16 ± 0.41 mm2 for Caucasian, 2.30 ± 0.56 mm2 for Chinese, 2.31 ± 0.41 mm2 for Filipino, 2.38 ± 0.40 mm2 for African and 2.40 ± 0.38 mm2 for Hispanic subjects. Age and spherical equivalent differed among the ethnic groups by Kruskal--Wallis test (p < 0.05). Sex differed among the ethnic groups by Chi-square test (p < 0.05). Ethnic differences in optic disc size were not observed among African, Hispanic, Filipino and Chinese subjects in linear mixed-effects regression analyses (p > 0.05). However, Caucasian differed from the other ethnicities in linear mixed-effects regression analyses (p < 0.05).Conclusions: Optic disc size was significantly smaller in Caucasian compared to the other ethnic groups. Optic disc size differences among non-Caucasian ethnic groups were not significant.