Purpose To study the correlation of visual acuity and the foveal photoreceptor layer in eyes with persistent cystoid macular edema associated with branch retinal vein occlusion (BRVO). Design Retrospective chart review. Methods We studied retrospectively the medical records of 42 eyes of 42 patients with persistent cystoid macular edema secondary to BRVO, eyes in which the foveal thickness was greater than 250 μm at final examination. On the vertical image obtained by optical coherence tomography at the final examination, we measured thickness of the foveal photoreceptor layer that was beneath the foveal cystoid spaces. We also assessed status of the junction between inner and outer segments of the photoreceptors (IS/OS) in the fovea. Results The photoreceptor layer beneath the foveal cystoid spaces was detected as a distinct layer with thickness varying between 33 μm and 124 μm (mean, 71.1 ± 26.8 μm). Final visual acuity showed no correlation with total foveal thickness ( r = 0.336, P = .092). However, it did show a close correlation with thickness of the foveal photoreceptor layer ( r = −0.571, P < .0001). Of the 42 eyes, 15 showed a continuous IS/OS line in the fovea. Visual acuity in these eyes with a continuous IS/OS line in the fovea was significantly better than that in eyes with a discontinuous or interrupted IS/OS line ( P < .0001). Conclusions Both the thickness and the integrity of the foveal photoreceptor layer are associated with visual function in eyes with persistent cystoid macular edema associated with BRVO.