The effect of illumination on the time to, and pupil area of, maximum mydriasis

This study was designed to evaluate the mydriatic effects of patients being dilated under differing illumination conditions. Twenty subjects, ten females and ten males had their pupils dilated under darkened conditions and under normal illumination to determine if there would be a difference in the rate of mydriasis, or overall pupil size at the point of maximum dilation. Iris color and gender were separately evaluated factors in dilation results. Subjects were dilated using one drop each of tetracaine 1%, phenylephrine HCI 2.5%, and tropicamide 1%. Pupil diameter was periodically measured using a Cogan\u27s pupilometer starting 6 minutes after drop instillation. Measurements with the pupilometer were taken at two minute intervals throughout the 30 minute test period. The final measurement 33 minutes after instillation of the dilating drops was taken with a biomicroscope reticule, both horizontal and vertical diameters were measured. No significant differences were seen between gender, iris color, or illumination type on the rate of maximum mydriasis. However, the relative pupil area was significantly greater following dilation under normal illumination conditions