This 65YO male presented with a branch retinal vein occlusion (BRVO) in his right eye and 20/40 vision. He was treated elsewhere about a year ago with 3 intravitreal injections and scatter laser 7 years earlier.
Pseudocolor SLO shows an old major inferotemporal ischemic BRVO, which arises from an arteriovenous crossing just inferior to the disc. Extensive collateral vessels bypass the occlusion and cross the temporal horizontal raphe. OCT scanning shows thinned, featureless inner retina (disorganization of retinal inner layers, DRIL). Scatter laser is noted temporally and inferiorly. OCT angiography shows variable capillary loss throughout the BRVO distribution and highlights the collateral vessels.
Learning Points:
Collateral vessels are dilated, pre-existing vessels that bypass an occlusion. These are most commonly seen in the posterior pole following retinal venous occlusions and are exceedingly rare with arterial occlusions. The endothelial tight junctions are intact, so they don’t leak angiographically. This helps differentiate them from neovascularization, which does leak.
DRIL is seen in various retinal vascular disorders, including diabetic macular edema and retinal vein occlusions. It is generally associated with worse vision and increased anti-VEGF treatment burden (see Babiuch et al, JAMA Ophthalmol 2019;137:38-46).
