Correlation between Retinal Nerve Fiber Layer Thickness Measured by GDx and Visual Field in Nonarteritic Anterior Ischemic Optic Neuropathy: A Comparison with the Contralateral Normal Eye

To evaluate the correlations between visual field (VF) defects with retinal nerve fiber layer (RNFL) thickness in nonarteritic anterior ischemic optic neuropathy (NAION) eyes, compare different GDx parameters with the other healthy contralateral eyes, and calculate receiver operating characteristic (ROC) curve for the GDx parameters Eighteen patients with unilateral NAION from at least 3 months before were enrolled. Patient's healthy eyes were considered as control. Peripapillary RNFL thickness was measured by GDx using variable corneal compensator (GDx VCC) and VF was tested using a central 24-2 program. The GDx measurements and VF test points were divided into 4 sectors and correlations of measured parameters for each nearly corresponding sector were evaluated. The two groups were compared in terms of RNFL thickness and VF sensitivity. Correlation of RNFL thickness and VF was calculated for each sector and ROC curve and sensitivities at specificity of >90% were calculated for each GDx parameter. All global and most sectoral GDx parameters were significantly different in affected and normal eyes. Temporal-nasal-superior-inferior-temporal (TSNIT) average, TSNIT standard deviation (SD) and nerve fiber indicator (NFI) were significantly correlated to mean deviation (MD) in NAION group (r=0.463, 0.597, -0.713; P=0.05, <0.01, 0.001 respectively). Most of the superior GDx parameters correlated well with the inferior field MD. Superior maximum had the highest sensitivity at ≥90% specificity at best cut-off point of 0.001 (100%). Most of GDx parameters were correlated with corresponding VF MD in eyes with NAION. Superior maximum was the most powerful discriminator between NAION and normal eyes.