Radial Peripapillary Capillary Density Measurement Using Optical Coherence Tomography Angiography in Early Glaucoma

Purpose: The purpose of the study was to compare radial peripapillary capillary (RPC) density between normal subjects and patients with early primary open-angle glaucoma (POAG) using optical coherence tomography angiography (OCT-A). Materials and Methods: A total of 24 patients with early POAG and age-matched 52 normal subjects underwent scanning with OCT-A imaging (RTVue XR-100, Avanti OCT). The enface angioflow images obtained were analyzed qualitatively for the RPC network, and RPC capillary density (CD) was measured in 8 sectors within a 3.45-mm-diameter circle around the optic disc, using the Bar-Selective Combination of Shifted Filter Responses (B-COSFIRE) method. CD and retinal nerve fiber layer (RNFL) thickness were compared between corresponding sectors with the Mann-Whitney U test. Correlations between CD and Humphrey visual field parameters and optic disc structural parameters were calculated by linear regression analysis. Results: In the normal eyes, RPC bed was clearly visible on OCT-A as a dense microvascular network around the optic disc, whereas in POAG patients it was focally attenuated. RPC CD was lower in the inferotemporal ( P =0.002) and superotemporal ( P =0.008) sectors with corresponding focal RNFL defect in POAG patients when compared with normal controls. The average CD correlated with visual field mean deviation ( P =0.01) and pattern standard deviation ( P =0.02) in glaucomatous eyes. Conclusions: OCT-A demonstrated reproducible, focal loss of RPCs in patients with early POAG when compared with normal controls. The results of our study suggest that the RPC density measurements may have a value in the diagnosis and monitoring of glaucoma.