Mydriasis and heredity

Routine ophthalmoscopy and fundoscopy of 673 individuals revealed 42 whose irides failed to dilate to a clinically useful degree within 25 to 30 min after the administration of drops of 1% mydracil. These individuals occurred with different frequency among the Aymara, Mestizo, and non‐Aymara groups which made up the sample of examinees. The phenomenon was most common among the Aymara, less common among the Mestizos, and least common among the non‐Aymara. Distribution of affected individuals within the three groups suggests that the trait is inherited.