Transient monocular visual loss is the most important visual symptom of arteriosclerotic vascular disease, arteritis and states of altered coagulability, and thrombocytosis. In most patients, the visual abnormality during each individual attack of visual loss is stereotypic. Visual loss occurrence is divided into four types. Type I is due to transient retinal ischemia, type II to retinal vascular insufficiency, and type III to vasospasm. Type IV occurs in association with antiphospholipid antibodies but includes cases of unknown etiology. Sudden monocular blindness is the major symptom of an ocular stroke causing permanent visual loss. The ocular strokes discussed are: central retinal artery (CRA) occlusion, ophthalmic artery (OA) occlusion, branch retinal artery (BRA) occlusion, and ischemic optic neuropathy (ION), which is the result of infarction of the optic nerve. Blindness can result from infarction of the retina or the optic nerve.