Driving is a nearly universal activity of daily living that depends heavily on rapid visual updating. Both transient and sustained visual disruptions have the potential to compromise safety. In this regard, contact lens wearers with low amounts of astigmatism may pose a unique problem for driving safety. Sometimes they are fit with spherical lenses, giving them a small sustained amount of blur from uncorrected astigmatism.
Other times they are fit with toric lenses, which improve on the spherical correction except during periods of lens rotation. Given that toric lens stabilization systems are continually being improved, is a relatively stable toric lens, such as the Acuvue® Oasys® for Astigmatism (AOfA), better than a spherical lens from a driving safety perspective? This study tests the hypothesis that astigmats wearing AOfA contact lenses, compared to spherical lenses, would lead to better driving-specific visual abilities and overall driving safety.
We used a within-subject, single-blind, cross-over, randomized design to evaluate driving performance in 11 young adults with mild astigmatism. Each participant drove our driving simulator with no correction, spherical correction, and toric correction with AOfA lenses. In our sophisticated, highly-immersive virtual reality driving simulator, we quantified basic operational driving abilities (e.g. dynamic vision, contrast sensitivity, peripheral vision) and tactical driving performance skills (e.g., steering, maintaining speed, braking).
As expected, corrected vision led to significantly better operational driving abilities (p<.001). Even though operational abilities were similar with spherical and AOfA lenses, AOfA lenses led to significantly safer tactical driving performance (p<.002). Surprisingly, the effect size is equivalent to that found when comparing the tactical performance of sober vs. intoxicated drivers in the simulator.
Given previous research showing that poor tactical performance in this driving simulator is predictive of future real-world collisions, these pilot data suggest that correcting astigmatism with a lens such as AOfA, as used in this study, may have larger than anticipated implications for driving safety.