Acute loss of vision with hypoplasia of the contralateral carotid artery.

We report a case of a young woman with acute loss of vision of the left eye. The first diagnosis of hypoplasia of the common carotid artery, internal carotid artery, and vertebral artery on the right side was made by means of magnetic resonance angiography. The ischemic optic nerve lesion was caused by a steal phenomenon from the left internal carotid artery to the right cerebral hemisphere with consecutive hypoperfusion of the left ophthalmic artery. Anomalies of the cerebrovascular system should be included in the differential diagnosis of acute loss of vision, even in young patients without cerebrovascular risk factors.