Touching the cornea enhances pharmacologic dilation of the pupil, mainly in the dark iris

Adequate pupillary dilation is often difficult to achieve in darkly pigmented persons when using standard dilating drops. To quantify the degree to which mild corneal disruption could enhance this dilation, we touched the cornea of one eye and then placed dilating drops in both eyes of darkly pigmented and lightly pigmented subjects. The touch was either standard Goldmann applanation tonometry or corneal reflex testing using a cotton-tipped applicator. Pupil diameter was measured using a video infrared pupillometer. The mean difference in pupil diameter between the touched and the control eye at 30 min was six-fold greater in darkly pigmented, compared to lightly pigmented, subjects. Touching the cornea by the method described herein appears to be a safe, useful technique for routinely enhancing pharmacologic dilatation of the pupil in persons who have dark irises.