PURPOSE: We aimed to investigate the relationship between the severity of metamorphopsia and the foveal microstructure measured with spectral-domain optical coherence tomography (SD-OCT) in patients with cystoid macular edema caused by branch retinal vein occlusion (BRVO-CME). METHODS: The study included 30 eyes of 30 patients with BRVO-CME. We examined visual acuity and the severity of metamorphopsia using M-CHARTS. Central foveal thickness, central retinal thickness at the fovea (CRT-1 mm), and macular volume were measured with SD-OCT software. The status of ellipsoid zone (EZ), external limiting membrane (ELM), outer retinal cyst, and inner retinal cyst was also evaluated. RESULTS: The mean metamorphopsia score was 0.77 ± 0.50, with 28 of 30 patients (93 %) having metamorphopsia (metamorphopsia score ≥ 0.2). The vertical metamorphopsia score (0.89 ± 0.54) was significantly higher than the horizontal metamorphopsia score (0.64 ± 0.53) (p < 0.005). The status of EZ and ELM was significantly associated with visual acuity, but not with the mean metamorphopsia score. The mean metamorphopsia score was significantly related to CRT-1 mm (p < 0.05) and the presence of inner retinal cyst (p < 0.05). CONCLUSIONS: The severity of metamorphopsia was significantly associated with central retinal thickness and the presence of inner retinal cyst.