Microvascular Rearrangement following Branch Retinal Vein Occlusion in Rats

Abstract

Abstract: : Purpose: To analyze the microvascular remodeling following transient branch vein occlusion in rats. Methods: Branch retinal vein occlusion was induced in pigmented rats by laser photocoagulation. Confocal microscopy of fluorescein-dextran filled vessels was performed 1, 3, 8 and 30 days after laser treatment (n=4 in each group). The changes in morphology and density of microvessels upstream of the occlusion site within each layer were evaluated by serial optical sectioning. Results: At day 1, dilation of venules and capillary closure in the intermediate and deep microvessel layers were present. Following repermeabilization at day 3, venule dilation and capillary closure areas showed transient aggravation, then only partially regressed. At day 30 capillary density was reduced by 24% in the deep layer and by 62% in the intermediary layer. At all time points the superficial layer remained unaffected. Control and sham-treated retinas showed no changes. Conclusions: Following transient vein obstruction, the deep microvessel layer at the level of the outer plexiform layer is the most severely affected by capillary closure while the superficial layer appears unaffected. Following reperfusion of the occluded vein, these microvascular changes only partially regress. This suggest that treatments aimed at repermeabilizing an occluded vein should be applied early in order to avoid permanent retinal damage.

Keywords: vascular occlusion/vascular occlusive disease • pathology: experimental • ischemia