Factors Affecting Repeatability of Assessment of the Retinal Microvasculature Using Optical Coherence Tomography Angiography in Healthy Subjects

Various factors can affect repeatability of optical coherence tomography angiography (OCTA) measurements, and they have not been studied sufficiently. We aimed to investigate the factors associated with the repeatability of automated superficial retinal vessel density (VD) and foveal avascular zone (FAZ) metrics acquired from OCTA. A total of 141 normal eyes from 141 healthy subjects were included, and two consecutive macular 6 × 6-mm angiography scans were performed. VD, perfusion density (PD), and FAZ of the superficial capillary plexus were calculated automatically. Reproducibility was assessed based on intraclass correlations (ICCs) and coefficients of variation (CVs). VD (ICC: 0.824, CV: 3.898) and PD (ICC: 0.845, CV: 4.042) over the entire 6-mm scan area showed better repeatability than VD (ICC: 0.752, CV: 17.470) and PD (ICC: 0.752, CV: 18.552) in the 1-mm scan, and with respect to the obtained FAZ metrics (ICC < 0.75, CV > 10.0%). Regression analyses showed that two factors, signal strength (p = 0.004) and average VD over the total 6-mm scan area (p < 0.001), were significantly correlated with the CV of the VD. Signal strength was associated with the repeatability of OCTA measurements and should be considered in the analysis of retinal VD and FAZ.