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

Abstract

This study was designed to evaluate the mydriatic effects of patients being dilated under differing illumination conditions. Twenty subjects, 1 a females and 1 a 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 colour and gender were separately evaluated factors in dilation results. Subjects were dilated using one drop each of 1% tetracaine, 2.5% phenylephrine HCI and 1% tropicamide. Pupil diameter was periodically measured using a Cogan pupillometer starting 6 minutes after drop instillation. Measurements with the pupillometer were taken at two-minute intervals throughout the 3 a-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 colour and illumination type on the rate of maximum mydriasis. However, the relative pupil area was significantly greater following dilation under normal illumination conditions