Our current study aimed to investigate the association of preoperative OCT parameters with visual function after vitrectomy surgery in eyes with epiretinal membrane (ERM). This study enrolled 33 eyes with ERM that underwent vitrectomy surgery. In addition to visual acuity (VA), metamorphopsia was measured pre- and postoperatively for each eye. Using the preoperative horizontal and vertical OCT images, SUKIMA (the gap area between the ERM and retinal surface) was measured respectively and the average of horizontal SUKIMA and vertical SUKIMA was used for the analysis. The associations of baseline parameters (age, axial length, preoperative central retinal thickness [CRT], inner nuclear layer [INL] thickness, ectopic inner foveal layer [EIFL] and SUKIMA) with postoperative VA, the change in VA, postoperative metamorphopsia and the improvement in metamorphopsia were investigated using multivariate regression analysis followed by the model selection. The result suggested that age and INL thickness were related to the postoperative VA, whereas age and preoperative CRT were significantly associated with the change in VA. In contrast, only SUKIMA was correlated with the postoperative metamorphopsia, whilst age, EIFL and SUKIMA were associated with the improvement in metamorphopsia. Measuring SUKIMA might be useful for predicting postoperative metamorphopsia and the improvement in metamorphopsia in ERM eyes.