Quantification of retinal microvasculature and neurodegeneration changes in branch retinal vein occlusion after resolution of cystoid macular edema on optical coherence tomography angiography.

To compare foveal avascular zone (FAZ) area and circularity, ganglion cell layer (GCL) thickness, retinal perfusion density (PD), and vessel density (VD) in eyes with branch retinal vein occlusion (BRVO) after resolution of cystoid macular edema (CME) to fellow control eyes and to correlate these parameters with visual acuity (VA).SD-OCTA scans (Zeiss Angioplex; Carl Zeiss Meditec Version 10) obtained on 32 eyes with BRVO after resolution of the CME with their fellow eyes used as controls were retrospectively evaluated. Parameters analyzed were FAZ size and circularity, PD, and VD in the superficial capillary plexus measured in the Early Treatment Diabetic Retinopathy Study (ETDRS) grid pattern using the automated algorithm. GCL thickness was generated from the Macular Cube 512 × 218 protocol. VA measured on the same day as OCTA examination was recorded.

The mean FAZ area was greater (P = 0.01) in BRVO eyes (0.239 ± 0.108 mm²) when compared with fellow eyes (0.290 ± 0.127 mm²). The FAZ was more irregular in BRVO eyes compared with fellow eyes (circularity index = 64.6 ± 12.8% vs 71.1 ± 10.8%, respectively, P= 0.03). GCL thickness was lower in BRVO eyes compared with control eyes (67.19 ± 27.71 vs 77.79 ± 6.41 respectively, P= 0.006). The mean VD and PD were significantly lower in the ETDRS outer ring in BRVO eyes (P = 0.04 and 0.038, respectively). On comparison of the affected quadrant with the unaffected quadrant in BRVO eyes, the affected quadrant had a lower outer PD (P = 0.04), outer VD (P = 0.04), and GCL thickness (P = 0.02). There was no significant correlation of VA with FAZ, VD, or GCL thickness (P >0.05).

FAZ is more irregular and enlarged, and GCL is thinner, in eyes with BRVO after resolution of CME especially in the affected quadrant suggesting neuronal degeneration as a sequela of BRVO. Both perfusion and VD are reduced in the quadrant affected by the BRVO demonstrating regional quantitative differences in the retinal microvasculature. These parameters may prove useful in monitoring the disease progression and treatment response.