Implications of Vision Testing for Older Driver Licensing

Objectives. A range of medical conditions can lead to visual impairments either through effects on the eye or the visual pathways and brain. The prevalence of visual impairment increases with age. Furthermore, research evidence has shown that aging is related to a number of other processes that can lead to changes in cognitive functioning and sensory perception that may adversely affect driving (Marottoli and Drickamer, 1993; Stelmach and Nahom, 1992). This combination of factors is thought to contribute to older driver crash risk (Hakamies-Blomqvist, 1993; Stutts et al., 1998). Licensing authorities are the primary entity responsible for monitoring the medical fitness of their license holders. While it is important for licensing bodies to identify drivers who have conditions that place them at a heightened risk for crashes, at the same time, they should not unfairly restrict the mobility of disabled or aging drivers. Therefore, it is important that the licensing criteria for visual fitness to drive are based on scientific evidence establishing their effectiveness and predictive value for poor driving performance and unaceptable crash risk. The aim of this paper is to assess whether current licensing guidelines are consistent with the available scientific evidence on the effect of visual impairment on driving with a specific focus on older drivers. Methods. This article describes current licensing guidelines for vision from selected Western jurisdictions and reviews the available scientific evidence on visual impairment and driving performance on which such licensing decisions are based. Results. The findings of the review indicate that the predictive values of the vision tests commonly used for licensing decisions by the selected authorities are inconclusive. Discussion. The functional attributes of vision currently assessed for licensing do not adequately explain unsafe driving performance. Differences were observed across vision requirements for the selected jurisdictions, possibly reflecting the equivocal and inconclusive findings linking specific visual functions and impairment with crash risk. Setting benchmarks or performance thresholds on selected visual tests may be problematic for older drivers in particular, who are most vulnerable to underperforming. Driving involves a complex set of skills, and it is proposed that decisions about vision for safe driving need to be considered in the context of the driver's overall health and other functional abilities.