Purpose This study was designed to examine the on-road driving performance of drivers with hemianopia and quadrantanopia compared with age-matched controls. Methods Participants included persons with hemianopia or quadrantanopia and those with normal visual fields. Visual and cognitive function tests were administered, including confirmation of hemianopia and quadrantanopia through visual field testing. Driving performance was assessed using a dual-brake vehicle and monitored by a certified driving rehabilitation specialist. The route was 14.1 miles of city and interstate driving. Two “back-seat” evaluators masked to drivers’ clinical characteristics independently assessed driving performance using a standard scoring system. Results Participants were 22 persons with hemianopia and 8 with quadrantanopia (mean age, 53 ± 20 years) and 30 participants with normal fields (mean age, 52 ± 19 years). Inter-rater agreement for back-seat evaluators was 96%. All drivers with normal fields were rated as safe to drive, while 73% (16/22) of hemianopic and 88% (7/8) of quadrantanopic drivers received safe ratings. Drivers with hemianopia or quadrantanopia who displayed on-road performance problems tended to have difficulty with lane position, steering steadiness, and gap judgment compared to controls. Clinical characteristics associated with unsafe driving were slowed visual processing speed, reduced contrast sensitivity and visual field sensitivity. Conclusions Some drivers with hemianopia or quadrantanopia are fit to drive compared with age-matched control drivers. Results call into question the fairness of governmental policies that categorically deny licensure to persons with hemianopia or quadrantanopia without the opportunity for on-road evaluation.

Mild Cognitive Impairment (MCI) involves subtle functional losses that may include decrements in driving skills. We compared 46 participants with MCI to 59 cognitively normal controls on a driving evaluation conducted by a driving rehabilitation specialist who was blinded to participants' MCI classification. Participants with MCI demonstrated significantly lower performance than controls on ratings of global and discrete driving maneuvers, but these differences were not at the level of frank impairments. Rather, performance was simply less than optimal, which to a lesser degree was also characteristic of a subset of the cognitively normal control group. The finding of significantly lower global driving ratings, coupled with the increased incidence of dementia among people with MCI and the known impact of dementia on driving safety, suggests the need for increased vigilance among clinicians, family members, and individuals with MCI for initially benign changes in driving that may become increasingly problematic over time.

Persons with hemianopic and quadrantanopic defects rated as safe to drive compensated by making more head movements into their blind field, combined with more stable lane keeping and less sudden braking. Future research should evaluate whether these characteristics could be trained in rehabilitation programs aimed at improving driving safety in this population.

In a small sample of drivers, mild to moderate peripheral visual field restrictions were adversely associated with specific driving skills involved in maneuvers for which a wide field of vision is likely to be important (however most were regarded as safe drivers). Further studies using similar assessment methods with drivers with more restricted fields are necessary to determine the minimum field extent for safe driving.