The impact of uncorrected astigmatism on night driving performance

To investigate the effect of uncorrected astigmatism on night driving performance on a closed-road circuit.

Participants included 10 drivers (mean age 24.4 ± 7.0 years), with low to moderate bilateral astigmatism (0.75-1.50 DC), who were regular contact lens (CL) wearers. Vision and night driving performance were assessed in a cross-over design with a toric CL and a best-sphere spherical CL. Binocular visual function measures included photopic and mesopic visual acuity (VA), contrast sensitivity (CS), mesopic motion sensitivity and glare tests (Mesotest^® II and Halometer). Night-time driving performance was assessed on a closed-road circuit, which included measures of sign recognition, hazard detection and avoidance, pedestrian recognition distances, lane keeping, speed and overall driving score.

Correction of astigmatism with toric CL significantly improved mesopic VA, photopic and mesopic CS, mesopic motion sensitivity, and reduced glare (p < 0.05), compared to the spherical CL; there were no significant effects of visual correction type on photopic VA. Correction of astigmatism using toric CL resulted in significant improvements in night driving performance, compared to driving with spherical CL, particularly for sign recognition, avoidance of low contrast hazards, increased pedestrian recognition distances and overall driving score (p < 0.05).

Correction of low to moderate levels of astigmatism had significant positive effects on night-time driving performance and related tests of visual performance. This has important implications for optical corrections to improve night road safety of drivers with astigmatism.