Longitudinal vasculature changes in branch retinal vein occlusion with projection-resolved optical coherence tomography angiography

Purpose To analyze vascular changes in branch retinal vein occlusion (BRVO) using projection-resolved optical coherence tomography angiography (PR-OCTA). Methods We reviewed 30 consecutive eyes of 30 cases with BRVO retrospectively. PR-OCTA was performed during the acute, intermediate, and remission phases when anti-vascular endothelial growth factor drugs suppress cystic changes. The main outcome measures were vessel density (VD) and retinal thickness changes in the superficial capillary plexus (SCP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). Results The VDs did not change longitudinally in the SCP and DCP during the follow-up period. The VD was significantly ( p = 0.0105) greater in the ICP during remission than the acute phase. The full retinal thickness (internal limiting membrane [ILM] to retinal pigment epithelium [RPE]) and inner retinal thickness (ILM to inner plexiform layer [IPL]) decreased significantly ( p = 0.0002 and p = 0.0014, respectively) during the follow-up period. When the inner retina was thinner than 117 μm, the VD in the ICP increased significantly ( p = 0.045) during the follow-up period. When the inner retinal layer did not become thinner, the VD in the ICP remained unchanged. Conclusion PR-OCTA showed the three distinct vascular plexuses in BRVO. The VDs remained unchanged during the follow-up period in the SCP and DCP but increased significantly in the ICP during remission. Inner retinal thinning might cause increases in the VD in the ICP because of projection artifacts and segmentation errors despite using PR-OCTA.