September 2009




Mapping effectiveness of vision screening efforts

by Maxine Lipner Senior EyeWorld Contributing Editor


Is testing preventing traffic injuries?

When you take the miles traveled into account, older drivers have the highest crash rates in the world, according to Ediriweera Desapriya, Ph.D., research associate, University of British Columbia, British Columbia Children’s Hospital, Vancouver, British Columbia. That said, in a recent January 2009 Cochrane Database System Review, he finds that there is currently no way to assess how effective vision screening tools linked to licensing are in curtailing such accidents.

It’s no secret that like their young counterparts, older drivers tend to get into the most trouble behind the wheel. “Younger people have high crash rates because they are taking higher risks; also they are not wearing seat belts and are drinking and driving,” Dr. Desapriya said. “Older drivers, by contrast, don’t take risks but because of their fragility they have high crash rates.”

In addition to slower reaction times and less back and neck flexibility hampering their ability to properly view their surroundings, vision itself certainly plays a key role here. “With the aging process vision is going to deteriorate,” Dr. Desapriya said. “That is the major reason why they have high crash rates compared to the other population.”

He sees this as an extremely relevant issue. “When older drivers want to drive we need to ensure that their vision is suitable,” Dr. Desapriya said. “We need to have a good assessment in place to make people aware that they may have a weakness in this way.”

Seeking randomized trials

Spurred on by this, investigators reviewed data from around the world pertaining to whether or not vision screening efforts could help older drivers to reduce crashes. “Unfortunately, we couldn’t find any good studies around this area,” Dr. Desapriya said. For Cochrane review articles, only randomized controlled trials are considered. “You can have 100,000 retrospective review and case-controlled studies, but the methodology is very weak,” Dr. Desapriya said. “Sometimes you have contradictory types of results.”

The importance of properly conducting such a study should not be taken lightly. There can be significant consequences to curtailing someone’s mobility, Dr. Desapriya points out. “Older people need to have the right to be mobile,” he said. “If you restrict their mobility that means that they are disconnected from the rest of the world.” This can be emotionally devastating for some. “When you restrict people’s right to drive they have higher rates of depression, mainly because they don’t have anything to do—they are confined to the house,” Dr. Desapriya said. “Therefore when you restrict someone’s driving privileges you need to have the correct tools in place.”

Considering the standards

There currently are no universal screening standards. In some areas of the United Kingdom, drivers simply have to read off the sequence on their own license plates in order to pass their vision screening. “When you have your car for 10 or 15 years you tend to memorize your number,” Dr. Desapriya said. “Is that a valid tool to say you can or can’t drive?”

Investigators here argue that such measures are not enough. Dr. Desapriya thinks that there needs to be sophisticated tools in place in licensing facilities that show how people really see and whether this is adequate for them to retain their driving privileges.

Even Snellen acuity tests used in the U.S. may not be enough. Dr. Desapriya suggests that the standard tool should be a useful field of vision test. “Compared to the Snellen test this is a very sophisticated test,” he said. With the test it is possible to assess visual limitations including those in the periphery that may hamper driving. Also taken into consideration are cognitive issues such as difficulty dividing attention or slower processing ability. “We are proposing that that be adopted all over the world as the correct tool to identify people’s ability to drive,” Dr. Desapriya said.

Overall, Dr. Desapriya thinks that much more needs to be done in this area. “We need to have a methodologically regarded study, such as a randomized, controlled trial in place to see whether intervention is effective [in preventing crashes],” he said. “We need to have globally accepted scientific tools that enable us to screen the driver’s vision or other physiologic capabilities to drive safely.” In cases where driving is restricted, this should not be done lightly. Society also needs to put in place alternatives for individuals. “When we restrict older people’s driving ability, we need to have alternative mobility options in place to allow them to move freely in society,” Dr. Desapriya said.

Editors’ note: Dr. Desapriya has no financial interests related to his comments.

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