Tadpole-shaped pupils caused by segmental spasm of the iris dilator muscle

Segmental spasms of the iris dilator muscle produce intermittent pupillary distortion. A study of 26 case histories (six previously reported and 19 reported for the first time) showed that the episodes are brief (lasting less than five minutes in 23 of 26 patients, less than two minutes in 18 patients, and less than one minute in eight patients) but can occur several times a day. The patients ranged in age from 24 to 48 years (the age of one patient was not known); five were men and 21 were women. Eleven patients had Horner's syndrome, four had Adie's tonic pupil, and eight had definite or probable migraine (another three had possible migraine). The episodes eventually stopped, leaving no serious sequelae. Focal application of phenylephrine produced a similar distortion in a normal human eye.