Automobile driving performance of brain-injured patients with visual field defects

The purpose of this study was to examine whether patients with visual field defects resulting from cerebral injury are handicapped in their driving ability, because visual field loss as assessed in standard perimetry is often the basis for withdrawal of a person's driving license. Driving performance was tested on a driving simulator to obtain standardized results and for safety reasons. The visual field was assessed both with standard automated perimetry and computer-based, high-resolution, qualitative perimetry. We investigated nine patients with purely cerebral field defects (mostly homonymous binocular defects) who had no further neuropsychological or ophthalmological deficits. Their performance (driving speed, reaction time, and driving error rate) was compared with that of a control group of ten subjects. We found no differences in any of the tested parameters between the visually impaired subjects and the normal participants. This suggests that individuals with visual field defects, including those who suffer from homonymous hemianopia, may perform as adequately as normal individuals in realistic driving scenarios. The perimetrically assessed visual field may, thus, be of limited value for the prediction of driving safety, and we conclude that patients who have field defects should not summarily be denied a driving license.