Midriaz - pupil dilation. Occurs when a spasm of dilatatore iris or paralysis of her sphincter (see Pupillary reflexes) in connection with damage to the nervous system, such as botulism (see), and also at action of certain drugs: zacapawanyi in the eye of the solutions of atropine, of scopolamine, the ingestion of drugs belladonna etc. When mydriasis, there is a slight decrease in visual acuity, difficult to read. The treatment should be aimed at addressing the causes of mydriasis.