Quantification of Diabetic Macular Ischemia Using Optical Coherence Tomography Angiography and Its Relationship with Visual Acuity

Abstract

To quantify foveal avascular zone (FAZ) area and macular vascular density objectively using optical coherence tomography angiography (OCTA) and to examine correlations with visual acuity in eyes with diabetic retinopathy (DR) in the absence of diabetic macular edema. Retrospective observational case series. Eighty-four eyes from 55 patients with DR and 34 control eyes from 27 age-matched healthy participants. All eyes underwent OCTA (RTVue-XR Avanti; Optovue, Inc, Fremont, CA). Integrated automated algorithms were used to quantify FAZ area and macular vascular density. FAZ area, vessel area density (VAD), vessel length density (VLD), and visual acuity. In each study eye, DR was classified as mild nonproliferative DR (NPDR; n= 32 [38%]), moderate-to-severe NPDR (n= 31 [37%]), or proliferative DR (n= 21 [25%]). Mean FAZ area was greater in diabetic eyes compared with control eyes both in the superficial (0.427 mm2 vs. 0.275 mm2; P < 0.001) and deep (0.616 mm2 vs. 0.372 mm2; P < 0.001) vascular networks. Mean VAD was lower in diabetic eyes compared with control eyes in both the superficial (49.44% vs. 55.09%; P < 0.001) and deep (56.65% vs. 61.32%; P < 0.001) networks. Mean VLD was also lower in diabetic eyes compared with control eyes in both the superficial (17.68mm-1 vs. 21.55 mm-1; P < 0.001) and deep (21.19 mm-1 vs. 24.38 mm-1; P < 0.001) networks. In all eyes, there was a statistically significant negative correlation between the logarithm of the minimum angle of resolution (logMAR) visual acuity and the vascular density in both the superficial (VAD, ρ=-0.52; VLD, ρ=-0.54; P < 0.001) and deep (VAD, ρ=-0.50; VLD, ρ=-0.50; P < 0.001) networks. A positive correlation was found between logMAR visual acuity and FAZ area in both the superficial (ρ= 0.29; P<0.01) and deep (ρ= 0.48; P < 0.001) networks. Automated quantitative algorithms allow for objective assessment of retinal vascular changes in eyes with DR that are correlated to visual acuity. These methods may prove useful in monitoring disease progression and identifying parameters that affect visual function.