En Face Image-Based Analysis of Epiretinal Membrane Formation after Surgery for Idiopathic Epiretinal Membrane

Purpose: To analyze en face epiretinal membrane (ERM) images constructed using swept-source (SS) OCT and to determine the incidence of ERM formation after ERM surgery and its effects on visual function. Design: Retrospective, consecutive observational study. Participants: Consecutive series of 73 eyes (71 patients) with idiopathic ERM that underwent vitrectomy with both ERM and internal limiting membrane (ILM) peeling. Methods: We retrospectively reviewed the data of the 73 eyes included in the study. During surgery, the ERM was removed as extensively as possible, and the ILM was removed such that the area of ILM peeling was at least larger than the parafoveal area. All patients underwent comprehensive ophthalmologic examinations, including assessments of best-corrected visual acuity and metamorphopsia, before and at 2 weeks and 6 months after the surgery. En face images constructed using SS OCT were used to investigate ERM formation. Main Outcome Measures: The incidence of ERM formation at 6 months after the surgery, effects of ERM formation on visual function, and the relationship between ERM formation and the extent of ERM and ILM peeling. Results: At 6 months after ERM and ILM peeling, 8 eyes (11.0%) showed ERM formation (formation group). Twenty eyes (27.4%) exhibited remnant ERM without ERM formation (remnant group), whereas 45 eyes (61.6%) showed no ERM (no ERM group). In both the remnant and no ERM groups, best-corrected visual acuity and metamorphopsia showed significant improvements after ERM surgery (both P < 0.01); these improvements were not seen in the formation group (P = 0.067 and P = 0.053, respectively). However, no significant differences were found in preoperative and postoperative best-corrected visual acuities and metamorphopsia among the 3 groups. In the formation group, ERM formation occurred only in the area with residual ILM. Most patients who underwent ILM peeling in which the area of the peeling covered the ERM belonged to the no ERM group (97.7%; P < 0.01). Conclusions: Epiretinal membrane formation does not affect visual function significantly when the area of ILM peeling is larger than the parafoveal area. When the ILM peeling area covers the ERM area, postoperative ERM formation can be prevented.