The vision and driving challenge.

D riving a motor vehicle is the primary and preferred mode of travel for adults in many countries around the world. It is hard for many of us to imagine life without the use of an automobile. Probably not well known is the fact that driving has a widespread impact on health and well-being. Driving cessation has been linked to many negative outcomes, including increased likelihood of depression and social isolation (1), reduced access to health care services (2), and increased risk of entry into long-term care (3). Controlling a vehicle is obviously a highly visual task involving visual sensory functions, such a spatial resolution, contrast sensitivity, and light sensitivity. Yet by themselves, visual sensory functions are insufficient for safe driving performance. Driving goes beyond visibility issues and depends on the time-sensitive gathering of visual information used to support decision making and motor behaviors. Controlling a vehicle takes place in a visually cluttered environment with many distractions and involves the simultaneous use of central and peripheral vision. As the vehicle moves through the environment, the visual world is rapidly changing. The driver is often uncertain as to when and where a critical event will occur. Thus, it should not be surprising that research to date (4) indicates that the most effective vision-screening test for identifying crash-prone drivers is not a visual sensory test but a visual processing speed test with divided attention components. As Johnson and Wilkinson (5) point out in this issue of the Journal, the useful field of view test, which embodies these stimulus and task components, shows great promise as a method for visually screening older drivers at high risk for automobile collisions. Studies are currently underway to establish its efficacy in large populations in screening and rescreening older drivers for licensure (6). Jurisdictions throughout the world have recognized the importance of enhancing public safety on the roadways, and in so doing, set requirements for obtaining a driver’s license. Visual acuity is the most common method for vision screening for licensure. Yet, as Yazdan-Ashoori and ten Hove (7) point out in this issue of the Journal, there is wide variability in the level of visual acuity required to pass a licensure test. This lack of uniformity is understandable since there is no scientific evidence indicating what visual acuity cut-point for a screening test is most effective. In setting a visual acuity standard, jurisdictions are left to historical precedent, consultation with ‘‘experts’’ or policy advocates, public opinion, and/or reliance on the fact that sight distances for highway signs are designed for drivers having at least 20/30 Snellen binocular visual acuity (8). What is needed are well-designed, population-based, prospective studies to establish the association between visual acuity and incident at-fault motor vehicle collision involvement. Such studies would provide the necessary data not only to establish predictive acuity cut-points for at-risk drivers but also whether any acuity cut-point provides predictive validity to enhance highway safety. Future research might also examine how visual acuity screening could be supplemented with other screening techniques such as contrast sensitivity, processing speed, and divided attention tests, which have a growing evidence basis for their relevance to driver safety (5,7,9). The ophthalmologist is often called on to render an opinion regarding driving safety in a patient with impaired vision. The patient or family members may have described incidents that prompt concerns about the patient’s own safety and the safety of other drivers and pedestrians. As Johnson andWilkinson (5) and Yazdan-Ashoori and ten Hove (7) point out, some states and provinces have mandatory