Quantifying Choriocapillaris Flow Deficits in Sickle Cell Disease using OCT Angiography

Abstract

Purpose : There is increasing evidence that choriocapillaris (CC) occlusions contribute to retinopathy in sickle cell disease (SCD). In this work we evaluated the association between CC flow deficits and SCD genotypes using OCT angiography (OCTA).

Methods : 76 SCD patients (genotypes: 19 HbSC, 48 HbSS, & 9 HbS) and 26 race-matched unaffected controls were imaged twice at baseline and 1 hour follow up using a clinical SD-OCTA device (Avanti RTVue-XR; Optovue). Ten parafoveal 3x3mm (304x304pixels) OCTA scans were obtained and averaged at each session (PMID: 32574351). A 3µm OCTA slab located 27µm below the Bruch’s membrane was used for CC flow deficit measurement (Fig. A1-2 & B1-2). First, the shadow of the large retinal blood vessels was removed from the CC OCTA slab. Next, pseudo flat field correction (radius=10 pixels) was performed to remove uneven brightness using ImageJ. Lastly, CC flow deficit with area ≥16 pixels was segmented on the binarized image using Analyze Particles plugin on ImageJ (PMID: 22930834). CC flow deficit percent area was then computed for each session.

Results : No statistical difference of CC flow deficit percent area was found between sessions (Wilcoxon Signed Rank test, p=0.248) with intraclass correlation coefficient of 0.85. However, locations of flow deficit areas varied between sessions, suggesting intermittent perfusion over time (Fig. A3 & B3). Median ± interquartile range of mean percent area in controls, HbSC, HbSS, and HbS were 0.00±0.06, 0.07±1.44%, 0.24±0.49%, and 0.16±0.68%, respectively. Statistically significant differences were observed among study groups (Kruskal-Wallis test, p<0.001). Pairwise comparisons showed statistically significant differences between controls and each SCD genotype (HbSC: p=0.037; HbSS: p<0.001; HbS: p=0.004). No statistical difference was found among SCD genotypes.

Conclusions : Our imaging and image processing approach offers good repeatability to quantify CC flow deficits in SCD. Our findings also reveal permanent occlusions and intermittent perfusion of CC in SCD patients. Monitoring these regions could enhance our ability to anticipate regions of higher susceptibility in SCD.

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