Influence of alpha-adrenoceptor blockade with thymoxamine on changes in pupil diameter and accommodation produced by tropicamide and ephedrine.

In a study in 12 healthy volunteers, local instillation of thymoxamine eye-drops (0.2%) completely reversed the mydriasis produced by ephedrine (5%) but not that produced by ephedrine (5%) together with tropicamide (0.5%). Small but significant changes in accommodation were found with ephedrine and reversed by thymoxamine, suggesting that they were mediated through alpha-adrenoceptor activity. The thymoxamine eyedrops were well tolerated.