Microvascular changes in experimental branch retinal vein occlusion.

Collateral vessel maturation and regional capillary nonperfusion were examined clinically and histopathologically up to 48 months after branch retinal vein occlusion (BVO) in a monkey model. Significant increases in endothelial density, but not pericyte density, were noted in both dilated and normal capillary caliber vessels in regions of collateral flow, independent of duration of BVO from 4 to 15 1/2 months. Patent capillaries in regions of hypoperfusion showed increased endothelial densities but decreased pericyte densities. Pericyte loss was independent of duration of BVO; however, endothelial density may normalize years after BVO in these vessels.