Widefield choroidal vascularity index analysis for swept-source optical coherence tomography (SS-OCT)

Abstract

Purpose : Changes in choroidal vasculature are related to multiple choroid-related ocular diseases such as diabetic retinopathy (DR) and age-related macular degeneration. Measurements of the choroidal vasculature is known as the choroidal vascularity index (CVI), which is calculated as the ratio of vascular volume to total choroidal volume. We developed a choroid segmentation and a CVI algorithm for SS-OCT widefield scans. In this work, the CVI of patients with DR and healthy eyes were analyzed.

Methods : The choroid segmentation algorithm for widefield scans was developed based on a novel deep learning DCT-network architecture (Bagherinia et al., IOVS June 2023, Vol.64, 1115). The CVI algorithm was adapted for widefield scans using previously published work (Zhou et al., Mitigating the effects of choroidal hyper- and hypo-transmission defects on choroidal vascularity index assessments using optical coherence tomography. Quant Imaging Med Surg 2022;12(5):2932-2946). The algorithm was performed on 6x15x15 mm scans (both eyes) from healthy (20 scans, 17 subjects) and DR (20 scans, 13 subjects) cases including severe, mild, and proliferative DR using PLEX^® Elite 9000 (ZEISS, Dublin, CA). The CVI was calculated for 3 mm area, and 6 mm, 9 mm, 12 mm, 15 mm rings, and 15 mm area centered at the fovea (Figure 1). The mean CVI for each region along with corresponding box plots were generated.

Results : Figure 1 shows a B-scan with overlaid choroidal segmentation boundaries including the analyses of regions used in this study. Figure 2 shows a table of CVI values (mean ± SD) for the rings and areas as well as corresponding box plots for healthy and DR groups. Notably, the DR group exhibited a significantly lower mean CVI relative to the healthy group in 3 mm area, 6 mm and 9 mm rings.

Conclusions : We proposed a method to measure the CVI for widefield scans using SS-OCT. We showed that the DR group exhibited a lower mean CVI relative to the healthy group. This study may suggest that changes in choroidal vasculature could be a valuable tool for DR diagnosis.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1: B-scan with overlaid choroidal segmentation boundaries (left), the rings and areas centered at the fovea on a choroidal en face (right).

 

Figure 2: Table of CVI values (mean ± SD) for the rings and areas (top) as well as the corresponding box plots (bottom) for healthy and DR groups. p-value for each region was determined from two-sample t-test.