Ethnic differences in normal retinal capillary density and foveal avascular zone measurements

Background The purpose of this study was to quantify retinal capillary density and foveal avascular zone (FAZ) area in healthy subjects according to their ethnicity, using optical coherence tomography angiography (OCTA). Methods In this cross-sectional study, all eyes underwent swept-source OCTA (Triton, Topcon, Tokyo, Japan). Macular OCTA scans (3 x 3 mm) were obtained in healthy white Caucasian and black African subjects. The FAZ area and capillary density in both the superficial (SCP) and deep capillary plexuses (DCP) were automatically measured using a custom-made software combining vessel binarization and skeletonization. Results Twelve eyes of 12 healthy Caucasians and 15 eyes of 15 healthy black Africans were included in the analysis. The mean FAZ area was significantly smaller, and the overall vessel density (VD) was higher in the SCP and DCP of Caucasians compared to black Africans. The mean FAZ area was 0.26 +/- 0.008 mm(2)in the SCP and 0.25 +/- 0.05 mm(2)in the DCP in Caucasians versus 0.33 +/- 0.08 mm(2)in the SCP (p = 0.01) and 0.37 +/- 0.1 mm(2)in the DCP (p = 0.03) in Africans. In the SCP and DCP, the mean VD was, respectively, 40.5 +/- 0.8% and 47.1 +/- 0.5% in Caucasians versus 34.3 +/- 1% (p = 0.008) and 40.6 +/- 0.9% in Africans (p < 0.001). Discussion/conclusion In the SCP and DCP, VD is lower in black Africans compared to Caucasians. In OCTA studies on vascular diseases, ethnicity-matched measurements from healthy subjects should be used for comparisons.