Tuesday, April 5, 2011

How aging vision may impact your driving?

Driving involves a complex combination of skills including vision, attention, motor coordination, and cognition. Of all these skills, however, vision plays one of the most important roles. Much of the incoming information received during driving is visual information. The amount of visual information relied upon is so great, with 90% of sensory information being visual, that some experts actually believe that visual information, apart from all other sensory information, would be enough to drive safely. With this in mind, it is easy to see that vision impairments can have significant impacts on safe driving.

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One of the most noticeable impacts of aging vision on driving is the need for increased lighting due to the changes in the variable lens and the pupil discussed in the section, Changes in Vision. This means that driving becomes even more dangerous for the elderly at night, when adequate lighting is usually unavailable. This change is so significant that many senior citizens choose to stop driving during the dark hours. Senior citizens' ability to drive safely is also influenced by age-related problems with glare. The elderly drivers experience more glare and take much longer to recover from glare than younger drivers. During this recovery time, senior citizens are effectually blind, making them unable to use the visual information necessary to make the quick and safe decisions necessary for driving. During the already problematic dark hours, the major source of glare is headlights from oncoming cars. During the day, glare results from the large amounts of natural light entering through the windows of the vehicle. Window tints and sunglasses may help to control glare, but will further limit the amount of light that enters the eye.

Research has shown that the age-related changes that best predict senior citizens' ability to drive safely are reduced stereo acuity(depth perception), reduced visual attention, and reduced size of visual field. The impacts of these changes on driving should be obvious. A reduction in depth perception means that senior citizens will have a harder time judging distance than younger drivers. Reduced visual attention impacts driving because senior citizens are less able to attend to the many stimuli involved in driving tasks. Of these three, the most impairing change may be the reduction of the visual field. While it is vital that drivers be able to see the road ahead clearly, it is just as important to see the surrounding areas. People with a reduced field of vision may not be able to see possible dangers, such as cars pulling onto the road, people, animals, or objects which may enter the road suddenly, or emergency vehicles in their peripheral fields of vision.

Reduced acuity influences the ability to drive in more subtle ways. One acuity-related problem in driving is the inability to read dashboard instruments. While some components use large print, like most speedometers, other components use font that may be too small for the elderly driver to read. Senior citizens who cannot easily read gas and temperature gauges may unknowingly put themselves in dangerous situations. Other automobile parts may also use print that is too small, such as radio and air conditioner controls. Elderly drivers may be unable to drive safely when attention is divided between the road and inside controls. Reading signs while driving can also present a challenge to the elderly. Senior citizens may need to slow their vehicles to read a road sign, which can put them at risk for an accident with faster traffic. If they do not slowdown, the risk may be smaller, but they cannot read the sign. Obviously, challenge of driving is not one that can be easily solved for the elderly.

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US State Rules on Aging Drivers

Currently, driving regulations are decided on a state-by-state basis. Although the standard vision requirement for most states is 20/40 in at least one eye with or without eyeglasses, the crucial variable of how often that measurement is updated with the Department of Motor Vehicles is, well, all over the map.

Here are some examples:
  • In Arizona, a lifetime license can be issued up to age 65, but applicants must come into a license office every 12 years to apply for a duplicate license and have their vision re-checked.
  • In Florida (where the standard vision requirement is only 20/70 in at least one eye with or without eyeglasses, presumably because of that state's large elderly population), applicants may renew by mail twice if they have a clean driving record and may not undergo vision screening for a period of 18 years.
  • In Iowa, initial and renewal drivers must take and pass a vision test to be licensed. The renewal cycle is every 4 years, up to age 70, when the renewal cycle is reduced to 2 years.
  • In Vermont, only upon initial application for a driver's license (but not upon renewal) must a vision test be given.

Yet the new reality of not only a growing senior population, but also the stuttering economy, which is forcing many to put off retirement and keep working into their 70s, is forcing states to rethink the rules...

USA Today reported that "California is analyzing results of a pilot project in which drivers who failed an initial written or vision test were required to take additional tests, sometimes including an eye exam and a road test." Further, "Maryland state law allows police, doctors, and residents, including relatives, to refer potentially unfit drivers to the Motor Vehicle Administration's Medical Advisory Board. Police refer about 700 people annually; about 60% of them are drivers over age 65."

In Maine, the interval between license renewals was shortened from six to four years after age 62 and a vision check is required with each renewal.

And a 2004 Florida law requiring that older drivers pass a vision test before getting their license renewed has helped cut the death rate among drivers 80 and older by 17%.

In general, there are still four different approaches among the US States to the vision checks among elderly drivers:
  • No vision screening required (Alabama, Connecticut, Kentucky, Mississippi, New Jersey, Oklahoma, Tennessee, Vermont);
  • Vision screening required for older drivers only (Georgia, Maine, Oregon, Pennsylvania);
  • Visual screening required for all renewal applicants, but more frequent screenings not required for older drivers (Alaska, Arkansas, Delaware, District of Columbia, Massachusetts, Michigan, Minnesota, Nebraska, New Hampshire, New York, North Carolina, North Dakota, Ohio, South Dakota, Texas, Washington, Wisconsin, Wyoming, West Virginia);
  • Vision screening required for renewal applicants; more frequent screenings required for older drivers (Arizona, California, Colorado, Florida, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Louisiana, Maryland, Missouri, Montana, Nevada, New Mexico, Rhode Island, South Carolina, Utah, Virginia).

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 Adapting to changes

Driving is not necessarily an all-or-nothing activity. Some programs exist to help elderly drivers adjust their driving to changes in their physical condition. AARP (the American Association of Retired Persons) sponsors the 55-Alive Mature Driver Program, which helps older people deal with issues such as how to compensate for vision problems associated with aging. And, the Association for Driver Rehabilitation offers referrals to specialists who teach people with disabilities, including those associated with aging, how to improve their driving.

There are many ways for elderly drivers to adjust so they are not a danger to themselves or others. Among them are:
  • Have regular eye exams. You should have your eyes checked annually after 60 years of age, to detect vision problems and eye diseases.
  • Wear eyeglasses while driving. Aging eyes often need correction, even if you've never worn glasses before. Beat blurry vision with prescription eyeglasses or, if you need less correction, inexpensive reading eyeglasses. Always use a current prescription, and avoid eyeglasses with bulky frames that restrict your peripheral vision.
  • Don't drive at night, or at dusk or dawn. This is especially important if you are sensitive to glare or need more light to be able to see clearly.
  • Keep your windshield and mirrors clean. You should also clean your headlights often.
  • Fight glare with minor adjustments. Set your seat height so you're able to see at least 10 feet of road in front of your vehicle. It doesn't sound like much, but this adjustment can really reduce the glare from oncoming headlights. You also should get into the habit of glancing to the lower right of the road ahead when driving past oncoming traffic. Do not wear sunglasses or tinted glasses to fight nighttime glare.

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  • Check your blind spots often. Turn your head frequently to adjust for any peripheral vision you've lost. Also, you can adjust your side mirrors to get rid of blind spots.
  • Drive only to familiar locations, where you have a lower pressure from unfamiliar routes and warning signs.
  • Avoid expressways (freeways) and rush hour traffic, when it is possible. Having more flexibility to your daily schedule you should strive for the less stressful driving hours.
  • Use extra caution at intersections. In a 2007 study, the IIHS found 40 percent of fatal collisions involving elderly motorists occurred at intersections. The most common reason for these crashes was a failure to yield, especially when making a left turn.
  • Leave plenty of time to get where they are going. Take your time to get safely to the destination. Be over-cautious, trying to anticipate other traffic participants’ potential moves. Remember, that your reaction might be slightly slower, than at your young years.
  • Don't drive alone, if that is possible, especially on unfamiliar routes. Having an extra pair of eyes will help you to assist with locating hidden warning signs, and finding your way with GPS or map instructions.

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