Recent reports have been attempted to evaluate, without obtaining a positive result, whether the reduction in size of the optic disc may influence the pathogenesis of central retinal vein occlusion. Cup/disc ratios in the fellow eye of 67 patients with branch retinal vein occlusion were compared with the ratios of 67 controls matched to cases for age, sex and refractive defect. There was no significant difference between cup/disc ratios of the two groups. These results suggest that the anatomical features of the optic disc are of no importance in the development of branch retinal vein occlusion.