Visual and Structural Differences in Idiopathic Epiretinal Membrane According to the Presence of Retinoschisis

Purpose: To present differences in visual acuity and macular structure before and after surgery in patients with idiopathic epiretinal membrane (ERM) according to the presence of retinoschisis. Methods: This retrospective observational study included 324 eyes with idiopathic ERM, that underwent pars plane vitrectomy with ERM and internal limiting membrane peeling, and were followed for more than 6 months. Subjects were classified into two groups according to the presence of retinoschisis using preoperative optical coherence tomography (OCT; group 1, ERM with retinoschisis; group 2, ERM without retinoschisis). Preoperative and postoperative macular structure changes and surgical outcomes were compared. Results: Group 1 included 61 eyes, and group 2 included 263 eyes. Group 1 had a significantly higher preoperative and final postoperative best-corrected visual acuity compared with group 2 (p = 0.01, p = 0.02). Preoperative disorganization of retinal inner layers (DRIL) was significantly less in group 1 than group 2 (p = 0.01). Preoperative central macular thickness was not significantly different between the two groups. However, postoperative central macular thickness was significantly lower in group 1 than group 2 (p = 0.02, p = 0.01, p < 0.01). The ratio of the inner or outer layer in the total retinal thickness before surgery was significantly smaller in group 1 than in group 2 (p = 0.02, p = 0.04). Conclusions: Preoperative visual acuity was better and the occurrence of DRIL was less in idiopathic ERM with retinoschisis than without retinoschisis. Postoperative visual and structural outcome was better in idiopathic ERM with retinoschisis than without retinoschisis. Retinoschisis may have played a role in reducing the tractional force given to the inner and outer retina.