Visual illusions associated with previous drug abuse.

We describe the visual illusions experienced by five patients with a history of previous use of hallucinogens, marijuana, or both. Symptoms included shimmering of images, illusory movement of images, visual perseveration of stationary objects, streaking of moving objects, and moving objects appearing as a consecutive series of stationary images. In all cases, the symptoms had persisted or recurred after periods of drug abstinence ranging from several months to several years. Despite thorough and repeated examinations and investigations, there was no evidence of neurologic ophthalmologic disease in these patients. When patients present with these and other visual illusions, a thorough drug history may afford the answer, provided that other recognized causes of these visual symptoms, such as migraine, epilepsy, and intracranial lesions have been excluded.