The Relationship between the Mydriatic Action of Ephedrine and the Colour of the Iris.

Introduction IT is well known to practising ophthalmologists that ephedrine is less effective as a mydriatic in subjects with deeply coloured irides than in those with light irides. This observation was first reported by Howard and Lee (1927), who stated that there was a distinct difference between Caucasians with light coloured irides and Chinese with dark irides, the former responding to smaller doses, and giving a larger mydriasis which developed more rapidly to equal doses. Chen and Poth (1929a, b) observed that ephedrine was considerably less active in dilating the pupils in Americans of African and Chinese descent than in white Americans. Barbee and Smith (1957) confirmed these findings with American negroes and found that among white Americans, those with hazel, brown, or black irides were less responsive than those with blue, grey, or green irides. However, Sattler (1927) reported that he saw no difference in the mydriatic response of brown, green, or blue irides to ephedrine in Europeans and in one negro subject. We were not able to find any other reports on the mydriatic actions of ephedrine in subjects with different coloured irides and from different ethnic groups, so we took the opportunity to make observations in African, Indian, Chinese, and European students living in a university hall of residence.