Sector pupil dilation with phenylephrine and tropicamide.

A comparison of sector pupil dilation produced with 2.5% phenylephrine and 1.0% tropicamide was carried out on nine subjects. We found that 2.5% phenylephrine produced a significant increase in the vertical as compared to the horizontal diameter at 10, 20, 30, 40, and 50 min after instillation of the drug with the maximum vertical diameter occurring at 40 min. The pupil diameter in the vertical and horizontal meridians before drug instillation was 3.7 mm +/- 0.2 (mean +/- SE) whereas at 40 min the vertical and horizontal diameters were 6.7 mm +/- 0.4 and 5.2 mm +/- 0.3, respectively. Instillation of 1% tropicamide produced equal dilation of the vertical and horizontal diameters, which was maximum at 40 min. Before drug instillation, the pupils were 3.7 mm +/- 0.2 (mean +/- SE) in both the horizontal and vertical meridians. At 50 min the pupil diameter was 7.0 mm +/- 0.2 in both meridians in the eye that received tropicamide.