Driving 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 and Wilkinson (5) and Yazdan-Ashoori and ten Hove (7) point out, some states and provinces have mandatory reporting laws. In the absence of such laws, professional societies such as the American Medical Association must remind physicians of the ethical responsibility they have in reporting at-risk drivers. There are several dilemmas here. Some physicians do not know what the vision standard is for their state. Most physicians may not be aware of their state's reporting laws or how to go about issuing such a report. And what are the legal protections for the physician in terms of patient privacy issues versus the duty to protect the well-being of the community? A great deal of continuing medical education is required here, and it should be done at the state or provincial level given the significant policy differences across these jurisdictions. Finally, lacking the necessary training and expertise, physicians often feel uncomfortable in making such decisions, which will have major consequences for patients and their families.
Recently, driving assessment and rehabilitative services have emerged within the United States and Canada, which are staffed by occupational therapists and/or certified driving rehabilitation specialists. These professionals have the educational background and experience to evaluate the potential for safe driving in persons with functional impairments. Rather than risk making an inappropriate recommendation to stop driving, or telling a patient that it is “ok to drive,” physicians now have the option to refer patients to these driving clinics for appropriate assessment. Unfortunately, in most instances, these driving fitness evaluations are not yet covered by health insurance and will be an out-of-pocket expense to the individual.
Although the number of driving assessment and rehabilitation clinics is increasing and driver rehabilitation is recognized as a subspecialty within occupational therapy, there are widespread differences in preferred practice standards for both assessment and rehabilitation. Once again, this stems from a lack of evidence-based research to determine the best predictors for future collision involvement and what visual and cognitive skills are critical for good driving performance. Comparative effectiveness studies can tackle these problems to determine whether the driving assessment clinics are efficacious as compared to the traditional approach of physician reporting to the licensing office.
So the bad news is that there is much to learn about what the visual and eye condition risk factors are for unsafe driving, what screening tests are best with what cut-points for identifying at-risk drivers, and what assessment and rehabilitation strategies have good patient and societal outcomes. However, the good news is that these are all fundamentally researchable questions that can be practically addressed with current clinical trial and epidemiological study designs and measurement techniques. All it takes now is the societal commitment to identify the financial resources to underwrite the research to address these questions, whose answers will impact the health and well-being of millions of drivers worldwide.
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