Vision screening of older drivers for preventing road traffic injuries and fatalities: Cochrane systematic review

Abstract

Assessed as up to date: 2013/09/26

Background

Demographic data in North America, Europe, Asia, Australia and New Zealand suggest a rapid growth in the number of persons over the age of 65 years as the baby boomer generation passes retirement age. As older adults make up an increasing proportion of the population, they are an important consideration when designing future evidence-based traffic safety policies, particularly those that lead to restrictions or cessation of driving. Research has shown that cessation of driving among older drivers can lead to negative emotional consequences such as depression and loss of independence. Older adults who continue to drive tend to do so less frequently than other demographic groups and are more likely to be involved in a road traffic crash, possibly due to what is termed the "low mileage bias". Available research suggests that older driver crash risk estimates based on traditional exposure measures are prone to bias. When annual driving distances are taken in to consideration, older drivers with low driving distances have an increased crash risk, while those with average or high driving distances tend to be safer drivers when compared to other age groups. In addition, older drivers with lower distance driving tend to drive in urban areas which, due to more complex and demanding traffic patterns, tend to be more accident-prone. Failure to control for actual annual driving distances and driving locations among older drivers is referred to as "low mileage bias" in older driver mobility research.

It is also important to note that older drivers are more vulnerable to serious injury and death in the event of a traffic crash due to changes in physiology associated with normal ageing. Vision, cognition, and motor functions or skills (e.g., strength, co-ordination, and flexibility) are three key domains required for safe driving. To drive safely, an individual needs to be able to see road signs, road side objects, traffic lights, roadway markings, other vulnerable road users, and other vehicles on the road, among many other cues—all while moving, and under varying light and weather conditions. It is equally important that drivers must have appropriate peripheral vision to monitor objects and movement to identify possible threats in the driving environment. It is, therefore, not surprising that there is agreement among researchers that vision plays a significant role in driving performance. Several age-related processes/conditions impair vision, thus it follows that vision testing of older drivers is an important road safety issue.

The components of visual function essential for driving are acuity, static acuity, dynamic acuity, visual fields, visual attention, depth perception, and contrast sensitivity. These indices are typically not fully assessed by licensing agencies. Also, current vision screening regulations and cut-off values required to pass a licensing test vary from country to country. Although there is a clear need to develop evidence-based and validated tools for vision screening for driving, the effectiveness of existing vision screening tools remains unclear. This represents an important and highly warranted initiative to increase road safety worldwide.

Objectives

To assess the effects of vision screening interventions for older drivers to prevent road traffic injuries and fatalities.

Search methods

For the update of this review we searched the Cochrane Injuries Group's Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE (OvidSP), Embase (OvidSP), PsycINFO (OvidSP) and ISI Web of Science: (CPCI-S & SSCI). The searches were conducted up to 26 September 2013.

Selection criteria

Randomised controlled trials (RCTs) and controlled before and after studies comparing vision screening to non-screening of drivers aged 55 years and older, and which assessed the effect on road traffic crashes, injuries, fatalities and any involvement in traffic law violations.

Data collection and analysis

Two review authors independently screened the reference lists for eligible articles and independently assessed the articles for inclusion against the criteria. If suitable trials had been available, two review authors would have independently extracted data using a standardised extraction form.

Main results

No studies were found that met the inclusion criteria for this review.

Authors' conclusions

Most countries require a vision screening test for the renewal of an individual's driver's licence. There is, however, lack of methodologically sound studies to assess the effects of vision screening tests on subsequent motor vehicle crash reduction. There is a need to develop valid and reliable tools of vision screening that can predict driving performance.

Author(s)

Desapriya Ediriweera, Harjee Rahana, Brubacher Jeffrey, Chan Herbert, Hewapathirane D Sesath, Subzwari Sayed, Pike Ian

Summary

Vision screening of older drivers to prevent road traffic injuries and deaths

Good vision is critical for safe driving performance. Because vision declines with age, and the percentage of older adults in the population is increasing, it has become more important to consider the vision screening requirements for older adults when designing evidence-based traffic safety policy. Mandatory vision screening for the issue or renewal of a driver's licence helps to ensure that older drivers are fit to safely operate vehicles.To date, there has been no trial to demonstrate the impact of vision screening on the prevention of older driver-related crashes. However, given the importance of good vision for safe driving, vision testing remains a relevant issue for all licensed drivers.

Reviewer's Conclusions

Implications for practice

At present, there is insufficient evidence to support or refute the efficacy of the vision screening test as a preventive strategy to reduce motor vehicle crashes among older drivers. In addition, the use of driving assessment tools, such as visual acuity, on road driving tests, simulator tests, and others vary among jurisdictions and their validity has been questioned in the research literature. Hence, further research is required to fully examine their reliability. In addition to licensing authorities, physicians also play a vital role in the safety of older drivers as they typically have the first encounter with older drivers experiencing vision problems. There is a serious need for research to develop a battery of tests with proven sensitivity and specificity for identifying high-risk drivers so that physicians and ophthalmologists can provide guidance to their patients, and also to medical advisory boards working with licensing offices (Hales 1982). Not only does research have the challenge of developing tests of high sensitivity and specificity for identifying unsafe drivers, these tests must also be cost-effective and acceptable to the public. In the interim, physicians should refer visually impaired drivers to driver training and re-education programs that are designed to reinforce safe driving practices and caution on the road.

Implications for research

There are no randomised controlled trials to demonstrate that vision screening for older drivers reduces the risk of motor vehicle crashes. Most countries require a vision screening test for driver licence renewal and this seems a reasonable and sensible approach. Good vision at all ages is important for safe driving. A case can be made, based on the existing literature, that more high quality trials are needed to evaluate the efficacy of vision screening in reducing motor vehicle crashes. Future trials would ideally utilise a randomised controlled trial design.

There is a need to develop effective vision screening tools that are valid predictors of fitness to drive. Vision standards established for driving licenses have been criticised for being arbitrary and not adequate to screen all potential visual components for safe driving (Ball 1988; Ball 1991; Levy 1995; Owsley 1998). Owsley 1991 and colleagues were the first to provide significant evidence that demonstrated a relationship between useful field of view (UFOV) and motor vehicle crashes. Performance-based functional assessments, including the use of driving simulators and road tests, may facilitate this task by providing information that is useful for the evaluation and rehabilitation of possibly impaired older drivers (Boegner 2004; Shope 1998; Underwood 1992). The UFOV concept has been further developed and used for training programs to help older drivers to retain and regain their driving skills.

UFOV is the area over which a person can extract information in a single glance without moving his or her head or eyes. The UFOV is shown to adequately predict driving performance. It provides a rapid and effective measure of visual information processing speed in approximately five minutes. It identifies examinees whose performance is associated with a significant increase in collision risk. UFOV also measures skills in selective and divided attention (Rizzo 1997) and how rapidly one can process multiple stimuli in the visual field. This measure is economically valid in that it has been shown to be an excellent predictor of both motor vehicle crashes and mobility outcomes among older adults (Ball 1998). Rinalducci 2002 showed that UFOV adequately predicted driving performance on a low-fidelity simulation task. Therefore, the UFOV may also serve as a useful method of identifying at-risk drivers who may not be easily screened through other techniques. Recent prospective studies have confirmed a relationship between UFOV performance and future crashes, further supporting the use of this instrument as a potential screening measure for at-risk older drivers (Rubin 2007). A recent meta-analysis conducted with numerous studies that included various methodologies confirms the importance of the UFOV assessment as both valid and reliable for indicating driving performance and for ensuring road safety (Clay 2005). This meta-analysis clearly demonstrated the association between poorer UFOV and poorer driving performance in older adults.

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