The effect of pupil dilation with tropicamide on vision and driving simulator performance

Purpose To assess the effect of pupil dilation on vision and driving ability. Methods A series of tests on various parameters of visual function and driving simulator performance were performed on 12 healthy drivers, before and after pupil dilation using guttae tropicamide 1%. A driving simulator (Transport Research Laboratory) was used to measure reaction time (RT), speed maintenance and steering accuracy. Tests of basic visual function included high- and low-contrast visual acuity (HCVA and LCVA), Pelli-Robson contrast threshold (CT) and Goldmann perimetry (FIELDS). Useful Field of View (UFOV - a test of visual attention) was also undertaken. The mean differences in the pre- and post-dilatation measurements were tested for statistical significance at the 95% level using one-tail paired t-tests. Results Pupillary dilation resulted in a statistically significant deterioration in CT and HCVA only. Five of 12 drivels also exhibited deterioration in LCVA, CT and RT. Little evidence emerged for deterioration in FIELDS and UFOV. Also, 7 of 12 drivers appeared to adjust their driving behaviour by reducing their speed on the driving simulator, leading to improved steering accuracy. Conclusions Pupillary dilation may lead to a decrease in vision and daylight driving performance in young people. A larger study, including a broader spectrum of subjects, is warranted before guidelines can be recommended.