OBJECTIVE To investigate the change in integrity and thickness of the foveal outer retina in eyes with chronic cystoid macula edema associated with retinal vein occlusion. METHODS We reviewed retrospectively the medical records of 30 eyes of 30 patients who had chronic cystoid macula edema associated with retinal vein occlusion and who had a follow-up of more than 12 months without any treatment. Using optical coherence tomography, we assessed the thickness of the outer retina and status of the junction between the inner and outer segments of the photoreceptors and of the external limiting membrane in the fovea. RESULTS Visual acuity showed a correlation with thickness of the foveal outer retina (R = -0.37) and with the detection of a line of the inner and outer segments of the photoreceptors (R = 0.65) and that of an external limiting membrane (R = 0.75) beneath the fovea. During the observation period (17.2 ± 5.5 months), neither visual acuity nor the condition of the foveal outer retina showed a significant change, and in no eyes were previously detectable lines of the inner and outer segments of the photoreceptors and external limiting membrane just beneath the foveal cystoid space became undetectable. CONCLUSIONS Even if a large cystoid space is located in the fovea, its effect on deterioration of the underlying foveal photoreceptor cells is not as strong as is generally thought.