Glaucoma Diagnostic Testing: The Influence of Optic Disc Size.

Abstract

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. The Bruch's 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. 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]). 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). 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.