To determine the effective minimal concentration of indocyanine green (ICG) for staining the internal limiting membrane (ILM) under air in macular surgeries and to report the clinical outcome of these patients.

Prospective, randomized clinical trial.

Consecutive cases of macular hole (17 cases) and epiretinal membrane (ERM) (11 cases) undergoing primary surgery with ICG-stained ILM peeling were randomized to receive one of the three concentrations (mg/ml) of ICG (1): 0.25, (2) 0.5, and (3) 1.25. The number of ICG injections, visual quality of the stained ILM, and time used for ILM peeling were recorded. Internal limiting membrane specimens were subsequently examined under electron microscopy. Preoperative and postoperative clinical data with fluorescein angiography were recorded.

There was a significantly smaller number of eyes with poor ILM staining in the 1.25-mg/ml group compared with the 0.25- to 0.5-mg/ml group (Fisher exact test, P = .04). The mean time required for ILM peeling was 4.2 minutes (range, 2.0–8.1 minutes). There was no significant difference in the time required for ILM peeling among the three concentration groups (one-way analysis of variance, P = .18) or between the macular hole and ERM group (two-tailed t test, P = .34). No ICG toxicity was found clinically or angiographically, except in one suspected case with ERM formation at the edge of ILM peeling. Electron microscopy of ILM specimens did not reveal any retinal elements.

1.25-mg/ml ICG under air stains the macular ILM consistently well for its removal in macular surgeries. The safety of ICG-stained ILM peeling needs further evaluation.