Collateral Vessels in Branch Retinal Vein Occlusion: Anatomic and Functional Analyses by OCT Angiography

Abstract

To analyze collateral vessels (CVs) associated with branch retinal vein occlusion (BRVO) anatomically and functionally using OCT angiography (OCTA). Retrospective review. Twenty-nine consecutive patients with BRVO. The distribution of the CVs 12 months after the onset of BRVO was studied using spectral-domain OCTA. En face 3× 3-mm OCTA images were acquired from 9 locations centered on the fovea and used to create a montage image of an 8.1× 8.1-mm square. The CVs were identified in 3 separate areas: the radial peripapillary capillary (RPC), superficial capillary plexus (SCP), and deep capillary plexus (DCP) layers. The numbers of CVs were evaluated in 4 regions: zone 1, the area within a 3-mm diameter circle centered on the fovea; zone 2, the area between the 3-mm diameter circle and its outer 6-mm diameter circle; zone 3, the area beyond the 6-mm diameter circle; and the temporal raphe. The relationship between the number of CVs and vessel density (VD) in each layer, persistent macular edema (ME) at 12 months, and the number of injections of anti-vascular endothelial growth factor (VEGF) agents. The number of CVs in zone 1 was correlated negatively (P= 0.0079) with the VD in the SCP, and the numbers of CVs in zone 3 and the temporal raphe were correlated negatively (P= 0.0017 and P= 0.036, respectively) with the VD in the DCP. The number of CVs in the RPC and total number of CVs were also correlated negatively (P= 0.0034 and P= 0.0113, respectively) with the VD in the DCP. In patients with persistent ME, the number of CVs in zone 1 was significantly (P= 0.0156) greater than in patients with nonpersistent ME and correlated positively (P= 0.025) with the number of anti-VEGF injections. The CVs in BRVO form as result of capillary dropout and are considered to represent remodeling of the retinal capillaries. The CVs around the fovea may be good indicators of persistent ME.