Change in the ophthalmoscopical optic disc size and shape in a 10-year follow-up: the Beijing Eye Study 2001–2011

BackgroundTo assess prevalence and associated factors of changes in the ophthalmoscopic optic disc size and shape.MethodsThe case–control study included all highly myopic eyes (myopic refractive error ≤−6.0 diopters) and a randomly selected group of non-highly myopic eyes, examined in the population-based Beijing Eye Study 2001 and 2011.ResultsThe study included 89 highly myopic eyes (age:65.0±9.8 years) and 86 non-highly myopic eyes. Reduction in ophthalmoscopic disc size (prevalence, high myopia: 30 (33.7%) eyes; non-high myopia: 7 (8.1%) eyes) was associated with non-circular gamma zone enlargement (OR: 19.4; 95% CI: 6.7 to 56.6; p<0.001) and disc-fovea line elongation (OR: 2.80;95% CI: 1.12 to 6.98; p=0.03). Disc size reduction was correlated with a disc diameter shortening in direction of the widest gamma zone enlargement (correlation coefficient r=34; p=0.01). The perpendicular disc diameter remained mostly unchanged, resulting in an ovalisation of the ophthalmoscopic disc shape. Enlargement of the ophthalmoscopic disc size (prevalence, high myopia: 22 (24.7%) eyes; non-high myopia: 4 (4.7%) eyes) was associated with circular gamma zone enlargement (4.99; 95% CI: 1.95 to 12.8; p=0.001) and high myopia (OR: 4.29; 95% CI: 1.34 to 13.8; p=0.01).ConclusionsMyopic axial elongation may lead first to a Bruch’s membrane (BM) opening (BMO) shift into the foveal direction leading to BM overhanging into the nasal intrapapillary compartment, development and enlargement of gamma zone at the temporal disc side, reduction in the ophthalmoscopically visible disc area and ovalisation of the ophthalmoscopic disc shape. In a second step, an axial elongation-associated BMO enlargement may lead to a circular gamma zone increase and, due to the retraction of BM at the nasal disc border, to an enlargement of the ophthalmoscopically visible optic disc.

Glaucoma Diagnostic Testing: The Influence of Optic Disc Size

Background There are various imaging techniques for the assessment of the optic disc in glaucoma patients. However, anatomically conspicuous, large or small optic discs can be quite challenging for an examiner. Objective The Bruchʼs membrane opening (BMO) by spectral domain optical coherence tomography (SD-OCT) is a modern approach for the quantitative measures of retinal nerve fibre layer (RNFL). The study focuses on comparison analysis of the BMO method and the widely used Heidelberg retina tomograph (HRT) method – in terms of detection of glaucoma for different optic disc sizes. Methods 216 Patients examinations during glaucoma consultation hours. Macro- (Ma) and micro-optic discs (Mi) detected by HRT are analysed via BMO analysis in SD-OCT. Correlation between BMO area and optic disc measured by HRT has been investigated and examined in terms of severity of visual field defect (MD [dB]). Results The results of study show that for micro and macro-optic discs there is a modest correlation between the size of optic disc measured by BMO and the size of optic disc measured by HRT by applying funduscopic examination (correlation rate r = 0,53; Mi: n = 111, Ma: n = 105). For micro-optic discs with a very small BMO area (< 1.5 mm2), there is a significant tendency (linear trend test p < 0.05) towards deeper visual field defects (MD < − 5 dB). Conclusion The BMO parameter of SD-OCT allows an assessment of glaucoma for a large range of optic disc sizes. BMO area and optic disc size measured by HRT are not correlated. Micro optic discs with a small BMO area lead to a higher risk of deep visual field defects.

Influence of Disc Size on the Diagnostic Accuracy of Cirrus Spectral-Domain Optical Coherence Tomography in Glaucoma

Purpose. To examine the influence of optic disc size on the diagnostic accuracy of optic nerve head (ONH) parameters determined by Cirrus spectral-domain optical coherence tomography (Cirrus HD-OCT). Methods. A total of 51 eyes of 51 normal participants and 71 eyes of 71 glaucoma patients were examined. ONH imaging was obtained by Cirrus HD-OCT. Sensitivity at a fixed 90% specificity along with the area under the receiver operating characteristic curve (AUC) for continuous parameters were analyzed. We also examined the coefficients of variation (CoV) for sensitivity estimates, as these have been used to test and quantify the influence of optic disc size on diagnostic accuracy. The influence of optic disc size on the glaucoma diagnosis was assessed by the likelihood ratio chi-square test. Results. Among the continuous parameters, the best diagnostic accuracy was seen for the average rim area, which had an AUC of 0.96. The most reliable factor across the disc size groups was the rim area (CoV, 2.8%). The diagnostic accuracy of the rim area did not appear to be influenced by optic disc size (P=0.17). Conclusions. The high diagnostic accuracy of the rim area demonstrated by Cirrus HD-OCT for the quantitative assessment of the ONH was not significantly affected by disc size in this study.