Measurements of cycloplegia and mydriasis induced by three common ophthalmic drugs

Abstract

The time course of the effects of three drugs on accommodation was assessed using conventional subjective methods and by an objective infra-red optometer, over a time period of up to three hours after drug instillation. Pupil diameter was monitored using the television display of the optometer. 1% and 0.5% Cyclopentolate, 0.5% Tropicamide and 10% Phenylephrine were separately employed on the same five subjects. The cholinergic antagonists Cyclopentolate and Tropicamide had similar initial time courses for both cycloplegic and mydriatic effects. Tropicamide typically produced incomplete cycloplegia with a short duration, and recovery was essentially complete after three hours. Cyclopentolate left only a small amount of residual accommodation of variable duration: the effects of the 1% and 0.5% concentrations employed were very similar. Subjective and objective assessments of amplitude of accommodation showed similar time courses. The adrenergic drug 10% Phenylephrine produced only a small cycloplegic effect of variable time course. Mydriatic effects of the cholinergic drugs showed similar initial time courses to the cycloplegic effects: no recovery occurred before the experimental session was complete. 10% Phenylephrine produced less mydriasis than the cholinergic drugs: the duration of the mydriasis was variable and recovery began within the experimental session. Intersubject variability occurred for both mydriatic and cycloplegic effects.