Mydriatic Response To Pharmacologic Agents

The term 'mydriasis' is used in at least two senses: a state of dilatation of the pupils (see 159420) and the process by which the pupils become dilated, as in response to a pharmacologic agent. Goldsmith et al. (1977) used the term in the latter sense in connection with their study of pupillary response to mydriatics in Chile. Among 673 persons tested they found 42 whose irides failed to dilate 'to a clinically useful degree' after a standard administration of a mydriatic. The frequency of nondilators differed among ethnic groups and the distribution within groups suggested that the trait is inherited. Mydriasis has been known to be more sluggish in persons with dark-colored irides than in those with light-colored irides. Bertler and Smith (1971) found concordance in pupillary responses in monozygotic but not in dizygotic twins. Hyperreactive mydriasis to atropine is a feature of Down syndrome (Harris and Goodman, 1968). (Paskind (1921) concluded that atropine had little effect in African American subjects, whereas in white subjects it produced an average slowing of 10 beats per minute.) In the rabbit, failure of the iris to respond to atropine is hereditary and reflects the presence or absence of atropinesterase (Sawin and Glich, 1943; Szorady, 1973).

One of the earliest studies of racial differences in mydriatic response to pharmacologic agents was that of Chen and Poth (1929). They found that Caucasians were most susceptible and African Americans least susceptible to the mydriatic action of cocaine, euphthalmine, and ephedrine; Chinese showed an intermediate response.