The ocular ischemic syndrome is caused by severely reduced ocular perfusion, usually secondary to carotid artery stenosis. Because of the low perfusion pressure, anterior chamber rubeosis does not invariably lead to increased intraocular pressure. The characteristic ocular pain is unrelated to the intraocular pressure. Patients adapt slowly to increasing light intensity (bright light amaurosis fugax). Retinal hemorrhages often lead to the mistaken assumption that the patient has diabetic retinopathy, especially when the patient has diabetes. A definite diagnosis is made by the demonstration of severely decreased ocular perfusion pressure. Supporting evidence is delayed filling on fundus fluorescein angiography in a patient with high-grade carotid artery stenosis. The majority of affected eyes lose vision for finger counting within one year. No treatment of documented value is available. Patients without neovascularization of the anterior chamber angle may occasionally experience improved vision after carotid surgery.