Anterior ischemic optic neuropathy is caused by microvascular occlusion of the prelaminar or laminar portion of the optic nerve head. The main types are arteritic, non-arteritic, and autoimmune. Few cases were reported following coronary artery bypass surgery. A 63-year-old man, who is both diabetic and hypertensive, underwent coronary artery bypass graft complicated postoperatively by sudden visual loss in his right eye. The diagnosis was non-arteritic anterior ischemic optic neuropathy. Possible predisposing factors were crowded disc and internal carotid artery stenosis.