Optimal dosage of cyclopentolate 1% for complete cycloplegia: a randomized clinical trial.

PURPOSE To determine the optimal dosage of cyclopentolate for adequate cycloplegia with minimal side effects. METHODS A prospective randomized clinical trial of patients 3.5 to 20 years of age referred to a strabismus clinic during a 1-year period. Eligible patients were randomly divided into three groups. In Group 1, the cycloplegic effect of one drop of cyclopentolate was compared with two drops; in Group 2, the effect of two drops was compared with three drops; and in Group 3, the effect of one drop was compared with three drops. RESULTS This study includes 192 eyes of 96 patients with a mean age of 11.0 +/- 5.7 years. Strabismus was present in 43 patients (44.8%). A total of 146 patients (76%) were hyperopic, 33 (17.2%) were myopic, and 13 (6.8%) were slightly hyperopic or myopic at the two stages of the study. Overall, only 16 eyes, including 9 eyes in Group 1 (16.4%), 2 eyes in Group 2 (3.2%), and 5 eyes in Group 3 (8.6%), had > or = 0.5 D difference in spherical equivalent refractive error at two stages of the study; however, intergroup differences were not statistically significant (p=0.16, chi-square test). Within each group, the percentage of eyes with <0.5 D difference was significantly greater than those with > or = 0.5 D difference (p<0.001 in all three groups, binomial test). Side effects were more prevalent using more frequent drops. CONCLUSIONS A single drop of cyclopentolate 1% suffices for cycloplegic refraction. There were less frequent side effects using one drop of cyclopentolate, compared to two or three drops.