Eligible patients who were scheduled for surgery for idiopathic macular hole (MH) were equally randomized to small extent group or large extent group depending on the extent of internal limiting membrane (ILM) to be removed. The ILM was peeled in round shape with the radius of either 0.75-disc diameter or 1.5-disc diameter according to the group. The primary analysis was conducted to identify the difference of functional and anatomical outcomes between the two groups. Subsequent analysis was performed to reveal the relationship between the functional and anatomical outcomes.