Influence of optic-disc size on parameters of retinal nerve fibre analysis as measured using GDx VCC and ECC in healthy subjects

Background To date, there is no knowledge on the impact of optic-disc size on the retinal nerve fibre layer (RNFL) as measured with GDx VCC or GDx ECC. Since the size of the optic disc is not taken into account for the analyses carried out by the GDx, it might affect sensitivity in large optic discs and specificity in small ones. Methods Topographic optic-disc measurements and RNFL thickness values of 80 healthy subjects were measured using HRT3 and GDx VCC and ECC. Subjects were divided into three equally large groups depending on optic-disc area. The authors used ANOVA to test the differences between groups of the GDx VCC and ECC parameters TSNIT average, superior average, inferior average and NFI. Results The mean optic-disc sizes of the three groups were 1.61, 2.00 and 2.61 mm(2). The optic-disc area did not significantly affect any of the tested RNFL parameters of the GDx and HRT3. For all HRT3 parameters of optic-disc morphology, ANOVA showed statistical significance between the three groups of different optic-disc areas. Conclusion The authors could not find any significant impact of optic-disc size on any RNFL parameter measured with GDx VCC or ECC and with HRT3.