Pruebas de visión en conductores de edad avanzada para la prevención de lesiones y muertes causadas por accidentes de tránsito
Resumen
Antecedentes
Los datos demográficos en Norteamérica, Europa, Asia, Australia y Nueva Zelanda indican un crecimiento rápido en el número de personas mayores de 65 años, ya que la generación Baby Boomer supera la edad de la jubilación. Debido a que las personas de edad avanzada constituyen una gran proporción de la población, se les considera importantes cuando se diseñan las políticas de seguridad vial futuras basadas en la evidencia, en particular, las que se refieren a restricciones para conducir o a dejar de hacerlo. La investigación indicó que dejar de conducir puede causar consecuencias emocionales negativas como depresión y pérdida de independencia en los conductores de edad avanzada. Las personas de edad avanzada que aún conducen tienden a hacerlo con menor frecuencia que otros grupos demográficos y existe una elevada probabilidad de que estén involucradas en un choque, probablemente debido a lo que se denomina "sesgo de bajo kilometraje". Los estudios de investigación disponibles indican que las estimaciones del riesgo de accidentes de tránsito de los conductores de edad avanzada según las medidas de exposición tradicionales son propensas al sesgo. Cuando se consideran las distancias anuales, los conductores de edad avanzada con distancias más cortas tienen un mayor riesgo de choque, mientras que los que recorren distancias más largas o promedios son más cuidadosos en comparación con otros grupos etarios. Además, los conductores de edad avanzada que realizan distancias más cortas tienden a conducir en zonas urbanas que, debido a patrones de tránsito más complejos y exigentes, son más vulnerables a los accidentes. En la investigación de la movilidad de conductores de edad avanzada la imposibilidad de controlar las distancias anuales reales y conducir en sitios con otros conductores de edad avanzada se denomina "sesgo de bajo kilometraje".
También es importante señalar que los conductores de edad avanzada son más vulnerables a lesiones graves y mortalidad en caso de un accidente de tránsito debido a los cambios en la fisiología asociados con el envejecimiento normal. La visión, la cognición y las funciones o habilidades motoras (p.ej. fuerza, coordinación y flexibilidad) son tres dominios clave necesarios para la conducción segura. Para conducir con seguridad, un individuo necesita poder ver las señales de la carretera, los objetos al lado del camino, los semáforos, las rotulaciones del camino, otros conductores vulnerables y otros vehículos en el camino, entre muchas otras indicaciones mientras conduce, con luz y condiciones meteorológicas variables. Es igualmente importante que los conductores tengan visión periférica para controlar los objetos y el movimiento para identificar las posibles amenazas mientras conducen. Por lo tanto, los investigadores coinciden en que la visión cumple una función significativa en la forma de conducir. Varios procesos y enfermedades relacionadas con la edad deterioran la visión, por lo que los exámenes visuales de los conductores de edad avanzada constituyen un tema de seguridad vial importante.
Los componentes de la función visual fundamentales para la conducción son la agudeza, la agudeza estática, la agudeza dinámica, los campos visuales, la atención visual, la percepción de profundidad y la sensibilidad al contraste. Generalmente los organismos que otorgan las licencias no evalúan completamente estos índices. Además, las reglamentaciones de las pruebas de visión actuales y los valores límites requeridos para pasar la prueba varían de un país a otro. Aunque hay una necesidad clara de desarrollar herramientas validadas y basadas en la evidencia para las pruebas de visión, la efectividad de las herramientas existentes no está clara. Lo anterior representa una iniciativa importante y muy justificada para aumentar la seguridad vial en todo el mundo.
Objetivos
Evaluar los efectos de las intervenciones de las pruebas de visión en conductores de edad avanzada para prevenir lesiones y muertes causadas por accidentes de tránsito.
Métodos de búsqueda
Se hicieron búsquedas en el registro especializado del Grupo Cochrane de Lesiones (Cochrane Injuries Group), en el Registro Cochrane Central de Ensayos Controlados (Cochrane Central Register of Controlled Trials, CENTRAL) (The Cochrane Library), MEDLINE (OvidSP), EMBASE (OvidSP), PsycINFO (OvidSP) y ISI Web of Science: (CPCI‐S & SSCI). Las búsquedas se realizaron hasta el 26 de septiembre 2013.
Criterios de selección
Se incluyeron ensayos controlados aleatorios (ECA) y estudios controlados tipo antes y después (before and after studies) que compararon conductores con 55 años y más a los que se les realizaron pruebas de visión con otros a los que no se les realizaron y que evaluaron el efecto sobre los accidentes, las lesiones, las muertes y cualquier infracción de tránsito.
Obtención y análisis de los datos
Dos revisores de forma independiente examinaron las listas de referencias de los artículos elegibles y evaluaron los artículos contra los criterios de inclusión. Si hubieran estado disponibles ensayos adecuados, dos revisores habrían extraído los datos de forma independiente mediante un formulario de extracción estandarizado.
Resultados principales
No se identificaron estudios que cumplieran con los criterios de inclusión para esta revisión.
Conclusiones de los autores
La mayoría de los países requieren pruebas de visión para la renovación de la licencia de conducir de un individuo. Sin embargo, no hay estudios metodológicamente sólidos para evaluar los efectos de las pruebas de visión sobre la reducción de accidentes automovilísticos posteriores. Es necesario crear herramientas para las pruebas de visión válidas y confiables que puedan predecir la forma de conducir.
PICO
Resumen en términos sencillos
Pruebas de visión en conductores mayores para prevenir lesiones y muertes causadas por accidentes de tránsito
Un buen estado de la visión es esencial para una conducción segura.Debido a que la visión se reduce con la edad y el porcentaje de personas de edad avanzada en la población está en aumento, al diseñar una política de seguridad vial basada en la evidencia se torna más importante considerar la necesidad de pruebas de visión para las personas de edad avanzada. La prueba de visión obligatoria para obtener o renovar la licencia asegura que los conductores de edad avanzada sean aptos para conducir con seguridad. Hasta la fecha no se han realizado ensayos para demostrar la repercusión de las pruebas de visión sobre la prevención de accidentes de tránsitos en conductores de edad avanzada. Sin embargo, dada la importancia de la buena visión para conducir de manera segura, las pruebas de visión aún son un tema relevante para todos los conductores autorizados.
Authors' conclusions
Background
In the early 1990s, the "Global Burden of Disease Study" predicted that traffic‐related injuries would become the third largest contributor to global death and disability by the year 2020 (Murray 1996). Treatment of people with injuries from road traffic crashes has a substantial impact on the healthcare system and wider society. In low‐ and middle‐income countries, between 30% and 85% of trauma hospital admissions are road crash victims. According to a survey completed by the Transport Research Laboratory (TRL), between 40% and 75% of the motor vehicle crash victims in developing countries were the principal earners in a family group (Silcock 1997). This has a direct impact on the gross national product (GNP), to the extent that injuries due to crashes cost low‐ and middle‐income countries between 1% and 2% of their GNP; more than the total development aid received by these countries (Murray 1996; WHO 2005).
The number of older drivers has and will continue to increase dramatically as populations worldwide continue to age. In the next three decades it is expected that there will be a huge increase in both the number of older people and the proportion of the population that they represent in almost all European countries as well as North America, Asia and Australia (Rosenbloom 2001). Data from the USA, Australia, Germany, New Zealand, Norway, and the United Kingdom demonstrate that, in spite of cultural and policy differences, older people today are more likely to have a driver's licence and will take more trips than a comparable group 10 years ago (Rosenbloom 2001).
People over the age of 65 years have more fatal crashes per mile driven than any other demographic group, except teenage males (NCIPC 2002). Available research shows that fragility and frailty are commonly associated with old age. Fragility refers to increasing inability to withstand disease or injury. Frailty describes the ability to recover from a disease or injury (Kent 2009). Due to the fragility of older persons, crashes more often translate to severe injuries and fatalities (Li 2003).
Earlier research maintained that older drivers do not have a higher risk per capita or per driver's licence, but their increased crash proneness is reflected in higher crash rates per driven distance (Hakamies Blomqvist 2005). It has been argued that older drivers, a group that drive small annual distances, have a higher crash risk per kilometre than other population groups with larger annual driving distances. Available research also suggests that older drivers' crash risk based on traditional exposure measures are prone to bias (Hakamies Blomqvist 2005; Janke 2001). Recent studies also confirm that self‐estimates of driving mileage on which these estimates depend are often inaccurate (Rizzo 2011). In general, failure to control older drivers actual annual driving distances and the actual driving locations are referred in the older driver mobility research as the "low mileage bias" (Janke 2001). Finnish, French, and Dutch motor vehicle crash data have shown, when compared across age groups, that older drivers had higher crash rates per distance driven. However, the age effect disappeared when the comparison was made in groups matched for yearly driving distance (Fontaine 2003; Hakamies Blomqvist 2002; Langford 2006). Recently, this effect was termed the "low mileage bias". This bias has been empirically demonstrated and shows that increased crash rates are due to driving exposure rather than age.
Description of the condition
As most individuals age, they experience some level of functional decline in sensory, physical, and cognitive function (OECD 2001). Age‐related changes in vision make it more difficult for older drivers to adapt to low light conditions, recognise road and road side objects under low lighting conditions and recover from glare. It has been suggested that the deterioration in vision that results from the normal aging process, as well as from eye disease, is likely to be a major contributing factor to the increased crash rates of older people (Wood 2001).
Vision is the most important source of information during driving and many driving‐related injuries have been associated with visual problems (Johnson 2010; Owsley 2010). Therefore, visual assessment for driving is paramount to the reduction of crash‐related injuries. Vision, cognition and motor functions are the three key functions required for safe driving (Desapriya 2008). Visual and cognitive tasks that are involved in driving include selective and divided attention and cognition. Researchers also believe that colour vision and glare sensitivity are important in driving. In addition, research has indicated that poor depth perception and peripheral vision are also associated with poor driving performance (Javitt 2002; Shope 1998; West 2003). Poor depth perception and peripheral vision affect ability to judge distance and speed. Further, studies have shown that many eye diseases affect vision and driving, for example cataract, macular degeneration, diabetic retinopathy, glaucoma, retinitis pigmentosa, corneal scarring, and eye movement disorders (Fishman 1981; Gutierrez 1997; Mangione 1998; McCloskey 1994; Owsley 1999). These conditions affect many aspects of vision including acuity, contrast sensitivity, visual field sensitivity, and increased disability glare. Disability glare is a degradation of visual performance caused by a reduction of contrast (Smith 2002).
Description of the intervention
Many types of interventions have been proposed to decrease the risk of motor vehicle crashes among older drivers, targeted toward the vehicle, the roadway, and the driver. In many countries, the primary driver‐related intervention focuses on re‐licensing requirements for older drivers, which may involve reassessment. Government policy employs a variety of methods for increasing the stringency of the licensure process for older drivers, including the adoption of in‐person renewal requirements, road tests, implementation of a shorter renewal period, and vision screening tests (Grabowski 2004).
Vision screening is a complex issue. While licensing authorities in many jurisdictions throughout the world use simple strategies to measure driving fitness, utilising simple visual acuity tests, it is not clear that the vision tests used actually assess the visual functions required to drive safely (Sivak 1996). Indeed, research has shown that visual acuity alone is not an appropriate method for assessing full visual function, which includes other vision components such as visual field and contrast sensitivity among others. Current vision screening testes utilised for licensing purposes mainly rely on assessment of visual acuity, which research suggests is, at best, weakly associated with traffic crash involvement (Awardzi 2009; McGwin 2008a). Therefore, more comprehensive vision testing, together with an evaluation of continuing competency for driving, is essential (Christie 2000).
New vision screening methodologies and standards for fitness to drive are now urgently required in order to promote road safety (Desapriya 2008). Evidence shows that visual field, body co‐ordination, and reaction time influence fitness to drive. A recent prospective cohort study conducted by the Motor Vehicle Administration (MVA) in Maryland, USA demonstrated a relationship between performance‐based risk factors and subsequent at‐fault crashes among older drivers (Ball 2006). The study concluded that a driver had to be physically, mentally, medically, and functionally fit in order to operate an automobile. Currently, these factors are not evaluated by licensing authorities.
The common standard threshold used for visual acuity is 20/40 (0.50, 6/12) and this is an accepted requirement for driving in many countries. However, this criterion varies from country to country, although most agree that visual acuity in the better eye of 20/40 (0.50, 6/12) is acceptable. For example, USA jurisdictions differ on the required minimum visual acuity and minimum visual field necessary to pass a screening test. Furthermore, some states assess colour vision, depth perception, contrast sensitivity, and disability glare, while others do not. It is interesting to note that the way in which visual acuity itself is measured differs among countries. For example, in North America visual acuity is measured by a Snellen’s chart in the driving licence office, while UK authorities simply ask a driver to read a number plate for visual acuity.
With respect to the renewal of a driver’s licence, there is also considerable variation. For example, jurisdictions across the USA differ in requiring road tests, vision screening, renewal in person, by mail or by the Internet (McGwin 2008). In Florida, drivers must demonstrate visual acuity of 20/70 in either eye, with or without corrective lenses, whereas drivers in Connecticut must have 20/40 in the better eye, with or without corrective lenses.
In some states, drivers who do not meet the vision requirement may be eligible for a restricted driver’s licence (Levy 1995). There is also variation among states with respect to the field of vision required to operate a motor vehicle. For instance, in Arizona the field of vision must be 60°, plus 35° on the opposite side of the nose, in at least one eye. The field of vision for Connecticut drivers must be 140° for a person with two eyes and 100° for a person with one eye (Owsley 1999). The age at which a vision test is required at renewal ranges from 40 years (Maryland) to 80 years (Virginia). Illinois and New Hampshire require a road test at renewal for drivers age 75 and older (McGwin 2008). This evidence illustrates that practices in the USA and many other countries that govern required vision screening and licensing of older drivers vary significantly. Given the extent of this variation, it is understandable that evidence relating to the effectiveness of vision screening is inconclusive:
Two retrospective cohort studies conducted in USA have suggested that vision‐related older driver licence renewal policies are associated with lower vehicle fatality rates (Levy 1995; Shipp 1998). However, another study, found no traffic safety benefits of vision‐related older driver licence renewal policies in the USA. An in‐person driver licence renewal policy yielded significant traffic safety benefits (Grabowski 2004).
The McGwin 2008a study found that the Florida 2004 mandatory vision screening re‐licensure law reduced the number of elderly drivers involved in fatal crashes by 17 per cent. In addition, this study showed that 93 per cent of individuals who sought licence renewal passed the current Florida vision test. The study suggests that future age‐related vision screening re‐licensing laws should target high‐risk drivers and safeguard driving privileges of low‐risk drivers. The 2008 study by McGwin and colleagues suggests that the Florida 2004 mandatory vision screening re‐licensure law is not a deterrent to seeking licence renewal for the ≥ 80‐year‐old population (McGwin 2008).
One recent review found that the re‐licensing policies requiring in‐person renewal, vision testing and the restricted driver licence were yielding traffic safety benefits for older drivers (Stav 2008).
A recent US study found that the older drivers from states with age‐related licence renewal polices had lower injury prevalence rates compared with drivers with licences from states without any licence renewal policies (Awardzi 2009). Similar to Grabowski 2004, this study also confirmed that the states requiring in‐person renewal had lower injury rates compared to states without in‐person renewal. However, this study found no traffic safety benefits related to reduced renewal cycles and vision/medical tests (Awardzi 2009).
Agimi 2013 found that the vision testing conducted during in‐person renewals are associated with lower fatal crash rates and lower hospitalisation rates. Vision testing was especially predictive of a lower crash fatality rate among drivers aged 80 to 84 and lower dementia prevalence among hospitalised drivers aged 60 to 69. However, this study found that the physician reporting requirements (mandated or legally protected) and length of licensing renewal had no traffic safety benefits. The public health significance of this available traffic safety literature is that the more restrictions on driving do not translate to lower crash rates among older drivers (Agimi 2013).
How the intervention might work
Self‐regulation helps older drivers modify their driving habits to suit their limitations, such as avoiding rush hour, daytime driving only and driving for essential trips only (e.g., groceries, doctors appointments) (Ragland 2005). Driving cessation has been shown to induce depression (Azad 2002; Marottoli 1997; Ragland 2005; Siren 2002) through a loss of independence (Fonda 2001); therefore, self‐regulation may be a feasible option that enhances quality of life and to facilitate safe driving for a greater number of years. However, self‐regulation cannot occur if a person is unaware that their actions require regulating. The goal of vision screening is to identify high‐risk drivers accurately and help them limit their driving. If older drivers are not screened, they may not be aware of their functional limitations. Proper valid screening, therefore, targets both road safety injury prevention as well as self‐awareness.
Researchers agree that the assessment of the driver’s ability should be a fundamental part of the solution for maintaining safe, older driver mobility (Eby 2007; Shope 1998; Staplin 1999). However, the tools that are currently available for licensing authorities to assess fitness‐to‐drive tend not to be scientifically derived or validated and rely heavily on subjective rather than objective conclusions (Eby 2007; Molnar 2007). There is a need, therefore, for the development of valid, evidence‐based instruments to aid licensing authorities in determining fitness to drive (Desapriya 2008; Desapriya 2009; Desapriya 2012). Clinically sensible screening and assessment tools are needed in order that licensing agencies can assess fitness to drive, and promote and facilitate safe licensing of older drivers (Eby 2007; Molnar 2007).
New vision screening methodologies based on evidence‐based practice and standards for fitness to drive are now urgently required to predict visual impairment and promote road safety (Hales 1982). Promising strategies to improve older adults’ driving performance to acceptable levels include: education, training, remediation of physical or mental disabilities, self‐regulation, or regulation by licensing authorities (Adler 2003; Dobbs 1997; Fox 1997; Roenker 2003; Shope 1998; Tuokko 1995). In particular, self‐regulation of driving has been proposed as a viable means of balancing older adults’ autonomy against the competing demand of public safety (Ball 1998; Shope 1998).
Why it is important to do this review
The safety of older drivers and others with whom they share the road is an important global traffic safety issue.The aim of this review is to evaluate the effectiveness of vision screening tests for the prevention of motor vehicle crashes involving older drivers. While vision screening assessments have generally been tested against on‐road driving performance, their impact on traffic crashes, road traffic law violation, fatalities, or injury reduction has not been evaluated. The effectiveness of vision screening for older drivers has been evaluated in retrospective cohort studies (see 'Characteristics of excluded studies'); however, the results are inconclusive as retrospective cohort studies are prone to bias. We therefore propose a randomised controlled trial (RCT) to evaluate the efficacy of vision screening in reducing crashes among older drivers.
Objectives
To critically assess the effects of vision screening interventions on the prevention of older driver‐related motor vehicle crashes
Methods
Criteria for considering studies for this review
Types of studies
Randomised controlled trials (RCTs) comparing crash rates among older drivers before and after vision screening interventions. Studies must have included one or more of the primary outcomes of interest: traffic violations, motor vehicle crashes, injuries or fatalities. In the absence of RCTs evaluating the effects of vision screening, controlled before and after (CBA) studies were also eligible for inclusion.
Types of participants
Trials with older individuals (aged 55 years or over) of either sex, who were current drivers.
Types of interventions
Any screening method, including road and vision testing, compared with controls without screening. This included tests such as 'useful field of view' (UFOV), contrast sensitivity, visual fields (central or peripheral), visual acuity, and any other automated vision screening measures.
Types of outcome measures
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Traffic violations.
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Motor vehicle crashes.
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Injuries sustained during motor vehicle crashes.
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Fatalities due to motor vehicle crashes.
Search methods for identification of studies
We did not limit our search by language, date or publication status.
Electronic searches
The Cochrane Injuries Group Trials Search Co‐ordinator searched the following:
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Cochrane Injuries Group's Specialised Register (26th September 2013);
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Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) (The Cochrane Library 2013, Issue 9 of 12);
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MEDLINE (OvidSP) (1950 to Sept 27th 2013);
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Embase (OvidSP) (1980 to 2013 week 39);
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PsycINFO (1806 to October week 1 2013);
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ISI Web of Science: Social Sciences Citation Index (SSCI) (1970 to Sept 2013);
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ISI Web of Science: Conference Proceedings Citation Index‐ Science (CPCI‐S) (1990 to Sept13).
Search strategies are listed in Appendix 1. Search methods for previous versions of this review are in Appendix 2.
Searching other resources
No other sources were searched for this update. See Appendix 2 for details.
Data collection and analysis
Selection of studies
Two review authors (SH, RH) independently reviewed titles (and abstracts where available) from the search outputs to identify potentially relevant studies. The same two authors independently reviewed the full text of studies identified, using a standardised inclusion criteria form. We resolved discrepancies through discussions between the authors, with the involvement of a third party (ED) where necessary. A list of excluded studies, together with details regarding the reasons for exclusion, has been provided in the table 'Characteristics of excluded studies'. We obtained full copies of those articles identified by the search considered to have met the inclusion criteria based on title, abstract, and subject descriptors.
Assessment of risk of bias in included studies
We planned to assess the quality of individual components, such as randomisation, allocation, concealment methods, blinding, and patient follow‐up. Key definitions derived from the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011) would have been used to assess the quality of selected studies. The elements inherent in a carefully designed and conducted RCT are intended to minimise bias, balance confounders, and produce the most reliable estimate of treatment effect. We planned to assess each included trial against a comprehensive checklist provided in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). Four review authors (HC, ED, JB, SH) planned to perform quality assessment independently, with disagreements being resolved by further discussion.
In the event of an absence of RCTs, we planned to consider controlled before and after (CBA) studies for inclusion. The following methodological criteria would have been used to assess CBA studies:
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study design;
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data collection methods;
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assessment of comparability of groups on potential confounders;
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sound method of ascertaining exposure (should be valid, reproducible, and blinded);
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sound case definition (should be valid, reproducible, and blinded);
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sound outcome assessment (should be valid, reproducible, and blinded);
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completeness of follow‐up.
Data synthesis
Where possible, we planned to calculate odds ratios (for categorical outcome data) or standardised mean differences (for continuous data) and their 95% confidence intervals (CI) from the data generated by each included RCT. If appropriate, and with available data, we planned to pool results from comparable groups of studies into a meta‐analysis using the RevMan 5.0 software provided by The Cochrane Collaboration (Review Manager). We intended to test heterogeneity between combined studies using the standard Chi2 test. Where statistical pooling was not appropriate or possible, we planned to provide a narrative summary of the findings.
Four review authors (HC, JB, SH, IP) planned to extract data independently using a standardised form. The following information was to be extracted:
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Type of study: RCT or CBA study.
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Study setting: road, time of year, and day when outcomes were measured.
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Type of screening: useful field of view (UFOV), contrast sensitivity, visual fields (central or peripheral), visual acuity, and any other automated vision screening measures.
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Follow‐up: duration of follow‐up from vision screening testing.
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Outcomes: number and types of older drivers committing traffic violations; involved in motor vehicle crashes; and sustaining minor, severe, or fatal injury.
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Cost: information about the cost of implementing vision screening.
Two review authors (HC, ED) planned to perform the applicable data analysis of the extracted data. The data would have been analysed as follows.
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Meta‐analysis: a random‐effects meta‐analysis would have been performed.
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Continuous data would have been analysed if means and standard deviations were available and there was no evidence of skew in the data (defined as mean > standard deviation). If scales measured the same outcome in different ways, standardised mean differences would have been combined across studies.
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Binary data: for studies with binary outcome data, the association between intervention and outcome would have been quantified using the odds ratio along with the 95% CI.
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Heterogeneity: investigation of the heterogeneity of the odds ratios across studies would have been assessed using a standard Chi2 test.
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Funnel plots: odds ratios would have been determined and represented on a funnel plot, which describes the relationship between effect size and study precision. We intended to examine the reasons for any relationship identified (sample size, publication bias, diversity of interventions and populations).
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Sensitivity analysis: the primary analysis would have involved all studies. We planned to assess the robustness of the findings by subgroup analysis based on sample size, study quality, and setting. Where possible, we planned to conduct high versus low‐ and middle‐income areas, and rural versus urban setting subgroup analyses, according to study context.
Results
Description of studies
In total we screened 5921 citations for eligibility: 4589 citations were screened in 2006; 756 citations in 2011; 576 citations were screened in 2013 (Figure 1). From the most recent search six relevant studies were identified but they did not meet the pre‐defined study design criteria.
Study flow diagram.
Risk of bias in included studies
No studies met the inclusion criteria.
Effects of interventions
No studies were identified that satisfied the inclusion criteria.
Discussion
We found no studies that met the inclusion criteria, and no studies are included in the review.
The major limitation of this review is that we were unable to find any high quality studies, such as randomised controlled trials or controlled before and after studies, to include in the review. Therefore, there is no definitive evidence in support of, or against, the hypothesis that vision screening leads to a reduction in motor vehicle crashes involving older drivers. A strength of this review is that it has identified a gap in the literature by demonstrating a lack of trials studying older driver vision screening and motor vehicle crashes.
Study flow diagram.
