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