EFFECT OF PROPARACAINE ON TROPICAMIDE-INDUCED MYDRIASIS

Purpose. The use of a topical anesthetic before the instillation of a mydriatic is recommended in order to enhance both the rate and magnitu de of pupillary dilation. However, there is a paucity of data supporti ng the prior use of topical anesthetics with tropicamide, the most com monly used mydriatic agent in optometric practice. Therefore, we condu cted a study to determine the clinical effect of proparacaine on tropi camide-induced pupillary dilation. Methods. We investigated the effect s of prior instillation of 0.5% proparacaine (Ophthetic) on pupillary dilation with 0.5% tropicamide (Mydriacyl) using a double-blind, place bo-controlled protocol on two groups of young adult subjects. Thirty s ubjects, aged between 18 and 30 years, were divided into 2 groups of 1 5, based on whether they had light- or dark-colored irides. The pupils of both eyes of each subject were dilated with tropicamide, but only one eye, chosen at random, received proparacaine (experimental conditi on), whereas the other was administered a saline placebo (control cond ition). Pupil diameter was measured using a ruler and magnifying loupe . Results. Subjects with light-colored irides had a greater average pu pil dilation than subjects with dark-colored irides. There was a small , statistically significant difference in pupil diameter between the c ontrol and experimental conditions, but only for subjects with light-c olored irides. The rate of pupillary dilation to peak pupil diameter a nd the rate of decrease in pupil diameter after peak pupil diameter wa s reached did not differ between experimental conditions or subject gr oups. Conclusions. Although prior instillation of topical proparacaine produced a statistically significant difference in pupil diameter for subjects with light-colored irides, the result was not clinically sig nificant. Therefore, we do not recommend the use of a topical anesthet ic before tropicamide-induced mydriasis for young adult patients.