Mechanisms of vision loss in eyes with macular edema associated with retinal vein occlusion.

Anti-vascular endothelial growth factor agents reduce macular edema and improve vision in eyes with macular edema associated with retinal vein occlusion (RVO), including branch RVO (BRVO) and central RVO. However, not all eyes with resolved macular edema show satisfactory best corrected visual acuity. Photoreceptor impairment can mostly explain the vision loss in these cases. Photoreceptor damage can be caused by subretinal hemorrhage in the central fovea and hard exudates or their precursor derived from concentrated lipoproteins originating from leaky retinal vessel extravasation. The contribution of neuron impairment in the inner retina, including the impairment of bipolar and ganglion cells by ischemia, indicated by the presence of a non-perfusion area (NPA), to vision loss in eyes with BRVO is insignificant. This is because the papillomacular bundle area is usually spared from NPAs in BRVO cases.