Cerebral complication after cardiac surgery with cardiopulmonary bypass varies widely focal neurologic deficit, stupor, coma, dementia, memory deficit, or seizures. The incidence of visual loss from ischemic optic neuropathy is from 0.06% to 0.113%. Visual loss is a rare but devastating complication of cardiac surgery. This report describes a patient who had reversible visual loss in postoperative period. She had undergone the decrease of bispectral index, cerebral oxygen saturation and the increase of suppression ratio during mitral valvuloplasty.