Characterizing collateral vessels in patients with branch retinal vein occlusions using wide-field swept-source OCT angiography

Abstract

Purpose : To date, optical coherence tomography angiography (OCTA) studies in retinal vein occlusions have primarily characterized collateral vessels (CVs) in the macula. The goal of this study was to use wide-field swept-source OCT angiography (WF SS OCTA) to characterize the morphology and functional significance of both macular and extramacular CVs in patients with a history of branch retinal vein occlusion (BRVO).

Methods : Twenty-eight eyes with a history BRVO were imaged using 12x12mm WF SS OCTA. CVs and non-perfusion area (NPA) were identified by two independent reviewers using ImageJ. Mixed effects multivariate regression analyses of factors associated with NPA and visual acuity were performed. Region of interest analysis of individual CVs was performed to identify correlations between CV size, depth and retinal location.

Results : Overall, 43% of eyes with BRVO showed evidence of collateral vessels on WF SS OCTA. Of these CVs, 55% were found in the macular region and 45% were extramacular. Analysis of collateral depth revealed that 87.3% of CVs coursed at least partly through the deep capillary plexus (DCP), while the remaining 12.7% of CVs were found to be strictly superficial. No CVs confined only to the DCP were identified. Pearson’s correlation analysis of individual collateral vessels revealed that CV depth increased with distance from the optic disc (r = 0.36, p = 0.007) and CV size increased with distance from the fovea (r = 0.38, p = 0.005). Multivariate regression analysis did not reveal statistically significant associations between CVs and NPA, or between CVs and visual acuity. Worse visual acuity (higher logMAR score) was associated with greater NPA (p < 0.001). NPA was in turn associated with greater central subfield thickness, a marker of macular edema (p = 0.022).

Conclusions : A large fraction of CVs that form after BRVO are extramacular, and the morphology of CVs varies as a function of retinal location. These results illustrate the importance of WF SS OCTA in BRVO, as heterogeneity in CV structure may correlate with distinct functional roles.

This is a 2021 ARVO Annual Meeting abstract.