To evaluate the clinical outcome and quantify histologically the amount of microscopic internal limiting membrane (ILM) and epiretinal membrane (ERM) present in ILM and ERM specimens obtained from ERM surgery.

Interventional consecutive case series.

Patients scheduled for ERM surgery were recruited prospectively. Pars plana vitrectomy, removal of ERM, and ILM peeling with indocyanine green (ICG) staining were performed in all patients. Epiretinal membrane and ILM specimens were sent for histologic examination. The amount of ERM present in ILM specimens and the amount of ILM present in ERM specimens were quantified by manual counting. Outcome measures include change in best-corrected visual acuity (BCVA), proportion of cases with 2 or more lines of visual improvement, anatomic outcome, proportions of microscopic ERM within ILM, and microscopic ILM within ERM.

Eighteen eyes in 18 patients were operated with a mean follow-up of 19.3 months. There were 13 primary ERMs and five secondary ERMs. The mean logMAR BCVA improved from 0.83 preoperatively to 0.49 postoperatively (P < .001). The mean lines of improvement in BCVA was 3.3 lines with 14 patients (77.8%) who had 2 or more lines of BCVA improvement. Histologic evaluation of the specimens showed no significant correlation with the final BCVA of 20/50 or better. Eleven (61.1%) of the ILM specimens showed various amount of microscopic ERM and 16 (88.9%) of the ERM specimens showed various amount of ILM fragments. The mean proportion of ERM within ILM specimens was 4.69% and that of ILM within ERM specimens was 51.5%. No significant recurrence of ERM was found.

Recurrence of ERM may be minimized by removing residual microscopic ERM present on the ILM. Indocyanine green-assisted ILM peeling in ERM surgery appears to have favorable visual and anatomic outcomes.