Retinal Microstructural Changes in Eyes With Resolved Branch Retinal Vein Occlusion: An Adaptive Optics Scanning Laser Ophthalmoscopy Study

Abstract

To assess macular photoreceptor abnormalities in eyes with resolved branch retinal vein occlusion (BRVO) using adaptive optics scanning laser ophthalmoscopy (AO-SLO). Prospective observational cross-sectional case series. After complete resolution of macular edema and retinal hemorrhage, 21 eyes (21 patients) with BRVO underwent full ophthalmologic examination and imaging with optical coherence tomography (OCT) and a prototype AO-SLO system. Cone density and spatial mosaic organization were assessed using AO-SLO images. Regular parafoveal cone mosaic patterns were clearly visualized with the prototype AO-SLO imaging system in the BRVO-unaffected side. However, in the side of the retina previously affected by the BRVO, cone mosaic patterns were disorganized and dark regions missing wave-guiding cones were apparent. Additionally, retinal capillaries were dilated, no longer had a uniform caliber, and had less direct paths through the retina. In the affected side, parafoveal cone density was significantly decreased, compared with the corresponding retinal area on the unaffected side (P < .001). Furthermore, the hexagonal Voronoi domain ratio and the nearest-neighbor distances were significantly lower than in the unaffected side (P < .05). These parameters were also correlated with photoreceptor layer integrity in the parafovea. After BRVO-associated retinal hemorrhage and macular edema resolved, affected parafoveal cone density decreases and the cone mosaic spatial arrangement is disrupted, becoming more irregular. These cone microstructural abnormalities may extend to parafovea in the BRVO-unaffected side.