Repeatability and Reproducibility of a Quantitative Assessment of the Retinal Vascular Network Fractal Dimension Measured With Swept-source Optical Coherence Tomography Angiography in Healthy Eyes

Abstract

Background: To evaluate the repeatability and reproducibility of the retinal vascular network fractal dimension (FD) measured from swept-source optical coherence tomography angiography (SS-OCTA) images of healthy eyes. Methods: A cross-sectional study was undertaken with young healthy volunteers who had no reported cardiac risk factors or ocular disease history. For each participant, three SS-OCTA images (12×12 mm) were acquired using the Cirrus Plex Elite 9000 (Carl Zeiss Meditec AG, Jena, Germany) by two ophthalmologists. The data from one eye per participant were retained for analysis. Automated segmentation was obtained from both the superficial and deep capillary plexuses. Fractal box-counting analyses were performed. The intraclass correlation coefficients (ICC) and the coefficient of variation (CV) were used as measures for repeatability and reproducibility. Results: A total of 43 eyes of healthy volunteers were included. The mean ± standard deviation (SD) age was 30 ± 6.2 years. The mean retinal vascular network FD was 1.693 in the superficial and 1.694 in the deep vascular layer in our healthy cohort. For repeatability, the ICC was 0.722 (95% CI, 0.541–0.839) in the superficial capillary plexus and 0.828 (95% CI, 0.705–0.903) in the deep capillary plexus. For reproducibility, the ICC was 0.651 (95% CI, 0.439–0.795) and 0.363 (95% CI, 0.073–0.596) at the superficial and deep capillary plexus, respectively. The CV for each observer was less than 5% in the two plexuses.Conclusions: In this study, the retinal vascular network FD provided new repeatability and reproducibility quantitative data using SS-OCTA with healthy participants.