Sudden short-lasting impairment or loss of vision. It usually affects only one eye, and is commonly due to local blood circulation disturbance. In its simplest form it occurs in normal people on rising suddenly from the sitting or recumbent position, when it is due to the effects of gravity. It also occurs in migraine. Transient ocular ISCHAEMIA may occur in the elderly as a result of blockage of the circulation to the retina (see EYE) by emboli (see EMBOLISM) from the common carotid artery or the heart. Treatment in this last group of cases consists of control of the blood pressure if this is raised, as it often is in such cases; and the administration of drugs such as aspirin that reduce the stickiness of blood platelets. In some instances, removal of the part of the carotid artery from which the emboli are coming may be advised.