Optical coherence tomography angiography evaluation of the fovea avascular zone.

Abstract

Purpose : To evaluate the size and characteristics of the foveal avascular zone (FAZ) in the superficial and deep capillary plexus in normal, healthy adults using optical coherence tomography angiography (OCTA).

Methods : In a prospective cohort study of 170 eyes, healthy volunteers underwent OCTA scans. The FAZ from 3mm x 3mm scans was independently graded using the ImageJ software. Circularity represents the degree of resemblance of the area to a perfect circle (a value of 1.0 denotes a perfect circle).

Results : The mean age of participants was 22.7 years (21 – 30, SD± 1.5), with mean spherical equivalent of -4.3 D. Mean superficial FAZ area was 0.25 mm² (0.04 mm² – 0.48 mm²) while mean deep FAZ area was 0.38 mm² (0.12 mm² – 0.66 mm²). The deep FAZ was significantly larger than the superficial FAZ (p<0.001). When the left and right eyes were compared, the superficial and deep FAZ sizes correlated strongly (correlation coefficients of 0.94 and 0.89, respectively), with mean differences between eyes of 0.001 mm² (p=0.720) and 0.005 mm² (p=0.408), respectively. The mean circularity index was 0.81 (range 0.54 to 0.95) for the superficial FAZ, and 0.89 (range 0.76 to 0.97) for the deep FAZ. The mean Feret’s (maximum) diameter was 0.65 mm for the superficial FAZ and 0.78 mm for the deep FAZ (p<0.001), at Feret’s angle of 92.3^o for the superficial FAZ and 78.4^o for the deep FAZ.

Conclusions : Both the superficial and deep FAZ size varies significantly among healthy young adults. There is strong correlation between the areas of the superficial and deep FAZ, and between the contralateral eyes. Deep FAZ area and Feret’s diameter are significantly larger than the superficial FAZ.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.