Is tropicamide a more effective cycloplegic than cyclopentolate in children with dark irides

Background: Cycloplegia of dark irides is commonly achieved using a combination of cyclopentolate (1%) and tropicamide (1%). To date, no studies have compared the use of a cyclopentolate/tropicamide combination with the use of tropicamide alone to determine whether the cyclopentolate is necessary in dark irides. In addition this is the first study to use the interval between drops as a variable for cycloplegic effect. Methods: We compared 4 different drug regimens - cyclopentolate plus tropicamide with 10 second interval (cyclo/trop), tropicamide plus tropicamide with 10 second interval (trop/trop), cyclopentolate plus tropicamide with 5 minute interval (cyclo/5min/trop) and tropicamide plus tropicamide with 5 minute interval (trop/5min/trop). The different cycloplegic regimens were administered to 174 Singaporean Chinese children aged between 3 and 12 years old. Results: The 4 treatment groups all had similar differences in autorefraction after cycloplegia (mean 0.4D), with a slightly larger (but not statistically significant) difference with the 'trop/trop' combination. Residual accommodation measured by the 'push-up' method was least in the 'cyclo/5min/trop' group, followed closely by 'trop/cyclo'. The 'trop/trop' group had an average of 0.8D more residual accommodation than 'cyclo/5min/trop'. This was statistically significant, p=0.035). Conclusions: Tropicamide (1%) is safer and faster acting than cyclopentolate (1%). In people with dark irides it has a superior mydriatic effect and similar cycloplegic effect. The authors suggest that clinicians consider substituting cyclopentolate combinations with 2 drops of tropicamide for maximum cycloplegic effect in Chinese children and other races with dark irides in cases where atropine is not required. (author abstract)