Morphometrical evaluation of the choriocapillaris imaged by swept-source optical coherence tomography angiography

Purpose: To assess the reproducibility of quantitative morphometrical evaluation of the choriocapillaris imaged with swept-source optical coherence tomography angiography (SS-OCTA). Subjects and methods: This observational, cross-sectional case series included 35 eyes of healthy individuals and 32 eyes of 32 patients. Two images of the fovea were taken using SS-OCTA with 3x3 mm squares. Images of the choriocapillaris within 800x800 pixel squares centered at the fovea were analyzed morphometrically using open-source software "AngioTool" that applies a Gaussian recursive filter and multiscale Hessian enhancement. This program's vessel thickness and intensity parameters can be changed to aid vessel detection. We measured the pairs of images per eye with different parameter sets and calculated the intraclass correlation (ICC) for the morphometrical results. After determining the parameters that produced high reproducibility, we evaluated regional variations in 800x800 pixel mm squares within the fovea. Results: The ICCs for vessel area, total vessel length, vessel diameter index, and mean lacunarity were over 0.9 using the parameters of " vessel thickness" 3-4 and intensity 15 in the group including all subjects. When measurements were performed using these same parameter values, the vessel density and mean vessel diameter index were 60.5% and 19.1 +/- 0.389, respectively. Vessel density, vessel length, vessel diameter index, and mean lacunarity did not change significantly within an 800x800 pixel square centered at the fovea except for the 200x200 pixel square at the foveal center. Conclusion: SS-OCTA images of the choriocapillaris can be measured with high reproducibility by morphometrical evaluation using open-source software with multiscale Hessian enhancement. Such automated morphometric analysis can provide an objective evaluation of the choriocapillaris.