In Reply.—
Dr Hoffman's suggestion that one may find many of the visual disturbances that were described in my article1 in non-LSD—using persons is well taken. The diagnosis of the LSD flashback syndrome, like that of epilepsy, is primarily made by carefully obtaining a history. But before drawing such a conclusion, the clinician has the responsibility of excluding the possibility of potentially more dangerous and treatable conditions that appear as visual disturbances. These include anatomic lesions and infections of the brain, toxic and metabolic aberrations, deliria, dementias, disturbances of sleep and consciousness, and entoptic imagery arising from disorders within the eye itself.Among the non-LSD—using subjects in my study, there were two who reported eight and nine different types of visual disturbances, respectively. No diagnostic explanations could be found. The other control subjects reported five or less such disturbances. In addition, one non-LSD—using subject who was interviewed as a control for a