Reproducibility and differences in area of foveal avascular zone measured by three different optical coherence tomographic angiography instruments

This study was performed to compare the area of the foveal avascular zone (FAZ-area) obtained by three optical coherence tomography angiography (OCTA) instruments. This was a cross-sectional, non-interventional study of twenty-seven healthy right eyes. The superficial and deep FAZ-area was measured manually with three OCTA instruments: Triton (Topcon), RS3000 (Nidek), and CIRRUS (Zeiss). The intra-rater, inter-rater, and inter-instrument correlation coefficients (CC) were assessed. The intra-rater and inter-rater CC were significantly high for the superficial and deep FAZ-areas (P < 0.001). The inter-instrument CC (95% confidence interval) for the superficial FAZ-area was 0.920 (0.803-0.965) for Triton vs RS3000, 0.899 (0.575-0.965) for RS3000 vs CIRRUS, and was 0.963 (0.913-0.983) for CIRRUS vs Triton (P < 0.001). For the deep FAZ-area, the inter-instrument CC was 0.813 (0.633-0.910) for Triton vs RS3000, 0.694 (0.369-0.857) for RS3000 vs CIRRUS, and 0.679 (0.153-0.872) for CIRRUS vs Triton (P < 0.001). The superficial FAZ-area (mm(2)) was 0.264 +/- 0.071 with Triton, 0.278 +/- 0.072 with RS3000 and 0.257 +/- 0.066 with CIRRUS. For deep FAZ-area, it was 0.617 +/- 0.175 with Triton, 0.646 +/- 0.178 with RS3000 and 0.719 +/- 0.175 with CIRRUS. The FAZ-area from these instruments was clinically interchangeable. However, the absolute values of FAZ-area are significantly different among them. These differences must be considered in comparing the FAZ-areas from different OCTA instruments.