Long‐term repeatability of optical coherence tomography angiography parameters in healthy eyes

Purpose To determine the long‐term repeatability of optical coherence tomography angiography ( OCTA ) parameters in normal eyes. Methods We prospectively enrolled 104 normal eyes. Participants were divided into three groups based on differences in the signal strength ( SS ) of OCTA scans obtained at two visits at least 6 months apart: group 1, SS difference = 2; group 2, 1; group 3, 0. We measured a foveal centred scan area of 3 × 3 mm pattern. All measurements were performed twice at 5‐min intervals at the initial visit. The second measurements were performed at least 6 months later. Results In short‐term vessel density ( VD ) repeatability, the coefficient of variation ( CV ) ranged from 3.89% to 8.10% and the intraclass correlation coefficient ( ICC ) ranged from 0.785 to 0.941. In terms of long‐term repeatability, the CV was 5.39–12.62% and the ICC was 0.598–0.867. In group 1, the ICC s of the inner and full VD s were 0.194 and 0.221, respectively. In groups 2 and 3, the ICC s of the inner and full VD s were 0.611 and 0.603, and 0.763 and 0.765, respectively. The central VD s of all groups had high CV besides high ICC . Conclusions Optical coherence tomography angiography parameters showed good short‐term and reasonable long‐term repeatability in normal individuals. The differences in SS s between measurements affected such repeatability, so physicians should query the reliability of OCTA parameters when the differences in SS are 2 or more even when the SS is high.