Choriocapillaris analysis in non-human primates using SS-OCTA

Abstract

Purpose : To quantify the choriocapillaris flow voids on non-human primates using SS-OCTA.

Methods : A total number of 8 non-human primates were used for this study. OCTA images were acquired by a commercial prototype SS-OCT system (PlexElite, Carl Zeiss Meditec Inc). Each non-human primate was scanned by two different imaging protocols: 3×3 mm² and 12 × 12 mm² centered at the fovea. Repeatability test was performed on a subgroup of three monkeys (6 eyes) by repeating the scans three times within a 3-minute interval. The areas of non-perfusion, also called flow voids, were segmented with a structural, intensity adjusted, uneven illuminance-compensated algorithm and the new technique was compared to previously published methods. The effect of sampling rate on flow void detection was studied by artificially reducing the sampling rate with either neighborhood averaging or spatial pooling.

Results : The novel algorithm compensates the “dark” appearance of large choroidal vessels, and compared to the previously published methods, the novel algorithm provides the best reproducibility (intraclass coefficient = 0.95, P<0.001) on detecting the choriocapillaris flow voids. Reducing sampling rate is associated with increased detected flow void size but not flow void density, which is agreed by similar flow void density in the macular area detected by two protocols (7.14 ± 0.65 % vs. 8.47 ± 1.37 %, P=0.03). In keeping with histological data, the flow void density increases nonlinearly and monotonically from the fovea to the periphery: the density is ~6-8% near the fovea and reaches ~27% at a distance of ~10 mm from the fovea.

Conclusions : OCTA provides a non-invasive platform of studying wide field choriocapillaris characteristics in non-human primates in-vivo. The current algorithm can be applied to images obtained from patients with ocular diseases to study choroidal microvascular abnormalities.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.