Vision screening of older drivers for preventing road traffic injuries and fatalities
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
The objective of this systematic review is to critically assess the effects of vision screening interventions in older drivers for prevention of road traffic injuries and fatalities.
Background
The Global Burden of Disease Study conducted in the 1990s, predicted that traffic‐related injuries will become the third largest contributor to global death and disability by the year 2020 (Murray 1996). Road traffic injuries cost low and middle‐income countries between one and two percent of their gross national product, which is more than the total development aid received by these countries (WHO 2004).
The number of older drivers has and will increase dramatically as populations worldwide continue to age. In the next three decades, there will be a huge increase in both the absolute number and proportion of older people in the population, in almost all European countries, North America, Asia and Australia (Rosenbloom 2001). Data from the US, Australia, Germany, New Zealand, Norway and the UK demonstrate that in spite of cultural and policy differences, older people around the world are more likely to have a driver's license, take more trips, and do so more often as the driver of a vehicle than a decade ago (Rosenbloom 2001).
Older individuals, 65 years and over, have more fatal crashes per mile driven than any other group, except teenage males (NCIPC 2001). There is extensive and continually expanding international research literature on older drivers, reflecting concerns that projected increases in the older driver population will increase societal harm from motor vehicle crashes (Li 2003).
A recent BMJ editorial noted that two independent trends in many countries are likely to reverse some of the improvements that have been made in road safety. The first trend is the aging of the population and its impact on traffic injuries and fatalities in the world. The second trend is the increase in sport utility vehicles (SUVs) and its impact on overall traffic safety (Simms 2005).
Furthermore, the older population is aging itself, and as most individuals age, they experience some level of functional decline in sensory, physical and cognitive areas (OECD 2001). It has been suggested that the deterioration in vision with age that results from the normal aging process, as well as through eye disease, is likely to be a major contributing factor to the increased crash rates of the elderly (Wood 2001).
Many types of interventions have been proposed to reduce the risk of motor vehicle crashes among older drivers; they can be targeted at the vehicle, the roadway and/or the driver. The primary driver‐related intervention focuses on the re‐licensing requirement for older drivers in many countries, however this varies across jurisdictions, with most requiring some form of age‐based re‐assessment. Vision screening tests address what is currently considered to be a critical aspect of age‐related disability and poor driving performance, namely visual decline.
Vision is the most important source of information during driving and many driving‐related injuries have been associated with visual problems. Therefore, visual assessment for driving is paramount. The common standard threshold used for visual acuity is 20/40 (0.5, 6/12) and this is an accepted driving requirement in many countries. However, this criteria varies from country to country, but most countries agree that a visual acuity in the better eye of 0,50 (20/40; 6/12) is acceptable for driving. The evaluation of the vision screening test has been undertaken to test its ability to reduce the occurrence of motor vehicle crashes involving older drivers. While this intervention has generally been tested against on‐road driving performance, it has not been evaluated in terms of its impact on traffic crashes, injuries, fatalities and road traffic law violations.
Objectives
The objective of this systematic review is to critically assess the effects of vision screening interventions in older drivers for prevention of road traffic injuries and fatalities.
Methods
Criteria for considering studies for this review
Types of studies
Randomized controlled trials (RCTs).
Studies must include one or more of the primary outcomes of interest: traffic violations, motor vehicle crashes, injuries or fatalities.
In the absence of RCTs evaluating the effectiveness of vision screening, controlled before‐and‐after (CBA) studies will be included.
Types of participants
Drivers 55 years of age and over.
Types of interventions
Any screening method, including road and vision testing, as compared with controls with no screening, will be included. This includes tests such as useful field of view (UFOW), contrast sensitivity, visual fields (central or peripheral), visual acuity and/or any other automated vision screening measures.
Types of outcome measures
Studies will be included if any of the following was recorded as an outcome measure:
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Traffic crashes
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Traffic‐related injuries
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Traffic‐related fatalities
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Traffic law violations
Search methods for identification of studies
Electronic databases
We will search the following electronic databases:
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Cochrane Central Register of Controlled Trials;
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Cochrane Injuries Group Specialized Register;
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MEDLINE;
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EMBASE;
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CINAHL;
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ERIC;
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National Research Register;
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PsycINFO;
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SIGLE;
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Science (and Social Science) Citation Index;
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TRANSPORT (NTIS, TRIS, TRANSDOC, IRRD); transportation research and literature databases to identify relevant keywords contained in the title, abstract and subject descriptors. Terms identified in this way, and the synonyms used by respective databases, will be used in an extensive search of the literature
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ATRI (Australian Transport Index);
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Road Res (ARRB).
The search will be based on the following strategy adapted as appropriate to the specifications of each database;
1.explode "Vision‐Screening" / all SUBHEADINGS
2.explode "Vision‐Tests" / all SUBHEADINGS
3.explode "Mass‐Screening" / all SUBHEADINGS
4.explode "Vision‐" / all SUBHEADINGS
5.(vision or visual or field of view or contrast sensitivity or visual field or driving capabil*) in AB or TI
6.#4 or #5
7.#3 and #6
8.( ((vision or visual) near (test* or screen* or assessment*)) in AB or TI
9.#1 or #2 or #7 or #8
10.explode "Motor‐Vehicles" / all SUBHEADINGS
11.explode "Automobile‐Driving" / all SUBHEADINGS
12.explode "Accidents‐Traffic" / all SUBHEADINGS
13.(driver* or driving) in AB or TI
14.#10 or #11 or #12 or #13
15.#9 and #14
16.(AGE:MEDS = AGED) or (AGE:MEDS = AGED‐80‐AND‐OVER)
17.(aged or elder* or old or older or senior* ) in AB or TI
18.#16 or #17
19.#15 and #18
Handsearching
We will handsearch the following journals for relevant articles published from 2000 to 2006: Injury Prevention, Accident Analysis and Prevention, International Journal of Injury Control and Safety Promotions, and the Journal of Safety Research. In addition, we will scan the reference lists (from selected papers or topic reviews) for further potentially relevant papers.
Grey literature and unpublished studies
We will search the websites of traffic and road accident research bodies, government agencies, and injury prevention organizations for grey literature.
We will also check the published abstracts from the six World Conferences on Injury Prevention and Control, and contact experts in the field for help in identifying further studies.
In addition we will undertake a general internet search for relevant dissertation abstracts, grey literature, and conference proceedings.
The searches will not be restricted by language or publication status.
Data collection and analysis
Study identification and selection
Two authors (SS, ED) will independently screen the titles (and abstracts where available) identified by the searches. The full text of potentially eligible studies will be obtained. Again, two authors (SS, ED) will independently assess the studies for inclusion using a standardized inclusion criteria form. Discrepancies will be resolved through discussion, with involvement of a third party (KT) if necessary. A list of excluded studies, together with details regarding the reasons for exclusion and a comprehensive methodological quality appraisal will be provided.
Data extraction
Four authors (SS, ED, FR, JK) will independently extract data using a standardized form. The following information will be extracted:
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type of study: RCT, CBA;
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study setting: Road, time of year and/or day when outcomes were measured;
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type of screening: Visual acuity (VA), useful field of vision (UFOV), contrast sensitivity;
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follow‐up: Duration of follow‐up from vision screening testing;
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outcomes: Number and type of older drivers committing traffic violations, involved in motor vehicle crashes, and/or sustaining minor, severe or fatal injury;
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cost: information about the cost of implementing vision screening.
Quality assessment
Although no consensus exists as to how the quality of studies should be evaluated, there is an approach of ranking the studies in order of methodological quality. There are several tools for validating the primary studies and many are still being developed. However, currently there is no gold standard instrument for assessing the quality of studies.
Assessment of quality of RCTs
Quality of individual components such as randomization, adequate allocation concealment methods, blinding and patient follow‐up will be assessed. Key definitions derived from Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2005), will be utilized to assess the quality of selected studies. The elements inherent in a carefully designed and conducted RCT will minimize bias, balance confounders, and hence produce the most reliable estimate of treatment effect. Each included trial will be assessed against a comprehensive checklist presented in the Handbook. Quality assessment will be performed independently by four authors (SS, ED, SB and KT), with disagreements resolved by discussion.
Assessment of the quality of CBAs
In the event of an absence of RCTs, CBA studies will be considered for inclusion. The following methodological criteria will be utilized to assess CBA studies:
1) study design;
2) data collection methods;
3) assessment of comparability of groups on potential confounders;
4) sound method of ascertaining exposure (should be valid, reproducible and blinded);
5) sound case definition (should be valid, reproducible and blinded);
6) sound outcome assessment (should be valid, reproducible and blinded);
7) completeness of follow‐up.
Data analysis
Two authors (SS, ED) will perform the analyses on the extracted data, as follows:
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meta‐analysis. A random‐effects meta‐analysis will be performed (if studies report similar interventions, data are available, and results are statistically and clinically homogeneous);
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continuous data will be analyzed if means and standard deviations are available and there is no evidence of skew in the data (defined as mean>standard deviation). If scales measure the same outcome in different ways, standardized mean differences will be combined across studies;
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binary data. For studies with binary outcome data, the association between intervention and outcome will be quantified using odds ratios (ORs) along with the 95% confidence interval;
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heterogeneity. Investigation of the heterogeneity of the ORs across studies will be assessed using a standard chi‐square test;
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funnel plots. Plotting the ORs on a funnel plot will examine the relationship between effect size and study precision. The reasons for any relationship identified (sample size, publication bias, diversity of interventions, populations) will be examined;
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subgroup analyses. The robustness of the findings will be assessed by subgroup analysis based on sample size, study quality, and setting (for example, high versus low/middle‐income areas, rural versus urban setting).
If the data are not suited to meta‐analysis, we will discuss them in a narrative review.
Presentation
Strength of the body of evidence and effectiveness will be presented using graphs and tables. Attention will be focused on the identification and summary of important gaps in research and data for vision screening on older drivers' traffic safety.
Interpretation
Findings will be interpreted on careful evaluation of existing research according to the quality of research methods and study designs (SS, ED, SB, IP, KT).
The following external reviewers who are experts in older drivers' traffic safety research will be contacted in order to reach consensus on the final interpretation of results of our systematic review; David Hogan, Ann Dellinger, Shawn Marshall and Karlene Ball.
Dissemination
After publication of the completed review on Cochrane Database of Systematic Reviews, a manuscript for publication in a peer reviewed international journal in the field of injury prevention or geriatric health will be prepared. Further, local dissemination of results will be performed through fact sheets, brochures and reports (SS, ED, IP).
