The effects on pupil size and accommodation of sympathetic and parasympatholytic agents

The time-response effect of two currently used mydriatics, phenylephrine and tropicamide, were evaluated in 524 eyes. Four different types of dilating regimens were used: 2.5% phenylephrine, 10% phenylephrine, 0.5% tropicamide, and the combination of 2.5% phenylephrine and 0.5% tropicamide. The analysis indicated that the recovery from mydriasis occurs between 5.5 and 7.0 hours with 2.5% phenylephrine and at more than 7 hours with 10% phenylephrine. The 0.5% tropicamide induced rapid dilation, whereas the combined treatment, 2.5% phenylephrine plus 0.5% tropicamide, produced the largest maximum pupillary diameter. Tropicamide, alone or in combination, also produced a longer mydriatic effect, lasting more than 7.0 hours. The recovery from the cycloplegic effect of the mydriatics occurred between five and seven hours in the majority of patients, with tropicamide alone or in combination with phenylephrine requiring the most time to revert to normal ranges of accommodation. The findings in this study indicate that, in normal subjects, the recovery from the effect of mydriatic agents is longer than what is generally reported in the literature.