The patients who are diagnosed with idiopathic epiretinal membrane and scheduled to undergo epiretinal membrane removal will be treated with conventional vitrectomy and the epiretinal membrane will be removed. After removal of the epiretinal membrane, indocyanine green staining will be used to determine the internal limiting membrane (ILM) peeled off with the epiretinal membrane. (Group 1: spontaneous ILM peeling) If it is confirmed that the internal limiting membrane is not peeled together, the investigators determine whether the active Internal limiting membrane peeling is performed by 1:1 randomization immediately during surgery. (Group 2: Active ILM peeling, Group 3: no ILM peeling) The outcomes of the three groups will be compared.

Inclusion Criteria:

• Age equal to or older than 19 years
• Patients diagnosed with idiopathic epiretinal membrane and scheduled to undergo the epiretinal membrane removal surgery

Exclusion Criteria:

• Accompanied with retinal vascular disease or intraocular inflammation
• Prior treatment with vitrectomy in the study eye
• History of glaucoma