Measuring Glaucomatous Focal Perfusion Loss in the Peripapillary Retina Using OCT Angiography

Abstract

To measure low perfusion areas (LPAs) and focal perfusion loss (FPL) in the peripapillary retina using OCT angiography (OCTA) in glaucoma. Prospective, observational study. A total of 47 patients with primary open-angle glaucoma (POAG) and 36 normal participants were analyzed. One eye of each subject was scanned using an AngioVue (Optovue, Fremont, CA) 4.5-mm OCTA scan centered on the disc. En face nerve fiber layer (NFL) plexus angiogram was generated. With the use of custom software, a capillary density map was obtained by computing the fraction of area occupied by flow pixels after low-pass filtering by local averaging 21×21 pixels. The low-perfusion map is defined by local capillary density below 0.5 percentile over a contiguous area above 98.5 percentile of the normal reference population. The LPA parameter is the cumulative area, and the FPL is the percent capillary density loss (relative to normal mean) integrated over the LPA. Peripapillary retinal LPA and FPL. Among patients with POAG, 3 had preperimetric glaucoma and 44 had perimetric glaucoma, with visual field (VF) mean deviation (MD) of-5.14±4.25 decibels (dB). The LPA was 3.40±2.29 mm2 in those with POAG and 0.11±0.18 mm2 in normal subjects (P < 0.001). The FPL was 21.8%±17.0% in those with POAG and 0.3%±0.7% in normal subjects (P < 0.001). The diagnostic accuracy as measured by the area under the receiver operating curve was 0.965 for both LPA and FPL, with a sensitivity of 93.7% at 95% specificity. The repeatability as measured by intraclass correlation coefficient was 0.977 for LPA and 0.958 for FPL. The FPL had excellent correlation with VF MD (Spearman's rho = -0.843), which was significantly (P= 0.008) better than the correlation between NFL thickness and VF MD (rho = 0.760). The hemispheric difference correlation between FPL and VF (Spearman's rho = 0.770) was significantly (P < 0.001) higher than the hemispheric difference correlation between LPA and VF (rho = 0.595). The low-perfusion map and LPA and FPL parameters are able to assess the location and severity of focal glaucoma damage with good agreement with VF.