Optical coherence tomography angiography of the foveal avascular zone in diabetic retinopathy

To analyze foveal avascular zone (FAZ) dimensions and symmetry in patients with diabetic retinopathy (DR) compared to healthy controls using optical coherence tomography angiography (OCT angiography). OCT angiography was performed via an AvantiA (R) RTVue 100 XR OCT system (Optovue, Inc., Fremont, CA, USA) in patients with diabetes mellitus (DM) and healthy adults. A frame centered on the fovea was used for FAZ measurements. The borders of the superficial vascular layer were defined as 3 mu m below the internal limiting membrane (ILM) and 15 mu m below the inner plexiform layer (IPL), and for the deep vascular layer as15 mu m and 70 mu m below the IPL, respectively. Angles of maximum FAZ diameter were measured in all eyes by two graders. In healthy eyes (N = 25), the FAZ surrounding vascular arcades were intact, showing a vertical or horizontal oval symmetrical formation with a maximum diameter usually on the horizontal or vertical axis. Diabetic eyes (N = 29) presented with disintegrity of the vascular arcades, resulting in an enlarged FAZ. In the superficial layer, the mean horizontal FAZ diameter was significantly larger in the DR group (753 mu m +/- 272 mu m) than in the control group (573 mu m +/- 177 mu m, p = 0.029). The difference was even more pronounced in the deep layer, with a mean value of 659 mu m +/- 194 mu m in the control group and 1009 mu m +/- 342 mu m in the DR group (p = 0.001). Furthermore, in the superficial layer, the angle of the maximum FAZ diameter was 0A degrees (+/- 15A degrees) or 90A degrees (+/- 15A degrees) in 72.0 % of healthy eyes. In eyes with DR, the angle was 0A degrees (+/- 15A degrees) or 90A degrees (+/- 15A degrees) in only 6.9 % of cases, due to the irregular configuration of the FAZ. OCT angiography is capable of imaging retinal vasculature without dye injection. Our data suggest that it can detect disintegrity of the vascular arcades surrounding the FAZ, thus differentiating DM from healthy eyes. Vascular abnormalities were more pronounced in the deep vascular layer.