Motor Vehicle Collision Involvement among Persons with Hemianopia and Quadrantanopia.

Persons with homonymous quadrantanopia and hemianopia experience driving restrictions, yet there is little scientific evidence to support driving prohibition among persons with these conditions. This retrospective cohort study compares motor vehicle collision (MVC) rates among 27 current licensed drivers with hemianopic and quadrantanopic field defects, who were ≥6 months from the brain injury date with that of 27 age-matched drivers with normal visual fields. Information regarding all police-reported MVCs that occurred over a period of nine years was obtained. MVC rates per year and per mile travelled were calculated and compared using conditional Poisson regression. Drivers with hemianopia or quadrantanopia had more MVCs per mile driven compared to drivers with normal visual fields; specifically their overall MVC rate was 2.45-times (95% confidence interval (CI) 0.89-3.95) higher and their at-fault MVC rate was 2.64-times (95% CI 1.03-6.80) higher. This study indicates that drivers with hemianopia or quadrantanopia have elevated MVC rates. This is consistent with previous research despite studies showing wide individual variability from excellent to poor driving skills. Future research should focus on the functional and driving performance characteristics associated with superior driving skills and/or those that may be amenable to improvement via behavioral and/or engineering interventions.