Branch Retinal Vein Occlusion: A Possible New Anatomical Risk Factor

Abstract

Purpose: : In a branch retinal vein occlusion (BRVO), a vein bifurcation is often seen close to the occlusion site at an arteriovenous crossing (occluded AV ). The goal of this study is to determine if there is a relationship between the proximity of a vein bifurcation (VB) to the occluded AV and the occurrence of a BRVO.

Methods: : A case-control study was done based on data collected from fundus photographs performed on patients with a diagnosis of a single BRVO at St Michael’s Hospital between 2004-2009. A total of 263 BRVOs were identified and divided into two groups according to the localisation of the occluded AV: Group A had the occluded AV on a first-order vein (166) and Group B on a second-order vein (97). In each group, the presence of a VB within half-disc diameter of the occluded AV was recorded as well as the occurrence of the VB at the occluded AV. For controls, the same findings were recorded in the opposite arcade of the same eye (Control #1), and in the same arcade of the opposite eye (Control #2).

Results: : In Groups A and B, a VB within half-disc diameter from the occluded AV occurred respectively 62% and 79% of the time. In Controls #1 for Groups A and B, a VB within half-disc diameter from an occluded AV occurred respectively 48% and 61% of the time. In Controls #2 for Groups A and B, this finding occurred respectively 38% and 53% of the time. The differences between Groups A and B to all corresponding control groups were all statistically significant (P<0.05%). In addition, in both groups, a vein bifurcation was seen more repeatedly at the site of the occluded AV (A 39%, B 73%) than in Controls #1 (A 18%, B 36%) and Controls #2 (A 9%, B 36%). These differences were also all statistically significant (P<0.05%).

Conclusions: : In patients diagnosed with single BRVO, the presence of a vein bifurcation within a half-disc diameter of the occlusion site at an arteriovenous crossing was identified more frequently than in the controls. These results suggest that a short distance between a vein bifurcation and an arteriovenous crossing may be associated with an increased risk of developing a BRVO. Further studies are warranted to confirm these findings.

Keywords: blood supply • anatomy • imaging/image analysis: clinical