Influence of Optic Disc Size on the Diagnostic Performance of Macular Ganglion Cell Complex and Peripapillary Retinal Nerve Fiber Layer Analyses in Glaucoma

Abstract

Purpose: : To evaluate the influence of optic disc size on the diagnostic accuracy of ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (RNFL) analyses provided by spectral-domain optical coherence tomography (SD-OCT) in glaucoma.

Methods: : Forty-seven glaucoma patients and 30 healthy subjects were included. All patients underwent GCC thickness and RNFL thickness measurement (3.45 mm scan) by SD-OCT. One eye was randomly selected for analysis. Initially, receiver operating characteristic (ROC) curves were generated for different GCC and RNFL parameters. The effect disc area on the diagnostic accuracy of these parameters was evaluated using a ROC regression model. Subsequently, we arbitrarily chose 1.5, 2 and 2.5 mm² disc sizes (based on the normal distribution of our data) and calculated the predicted areas under ROC (AUCs) for each of them.

Results: : Average MD for glaucomatous eyes was -6.1±5.2 dB. Similar AUCs were found for the best RNFL (average thickness=0.892) and GCC parameters (superior thickness=0.847; p=0.14). The coefficient representing disc area in our ROC regression model was not statistically significant for average RNFL thickness (-0.176) or average GCC thickness (0.088; p≥0.56). AUCs for fixed disc areas (1.5, 2.0 and 2.5 mm²) were 0.904, 0.891 and 0.875 for average RNFL thickness and 0.834, 0.842 and 0.851 for average GCC thickness, respectively.

Conclusions: : Diagnostic accuracy was similar between RNFL and GCC thickness parameters. Although not statistically significant, there was a trend for a better diagnostic accuracy of peripapillary RNFL thickness measurement in cases of smaller discs. For GCC analysis, an inverse effect was observed.

Keywords: imaging/image analysis: clinical • optic nerve • ganglion cells