Night Vision Problems and Driving?>

Night Vision Problems and Driving

by Berkeley Wellness  

If you have more diffi­culty seeing when you drive at night than in the day, you’re hardly alone. But it’s not something to be taken in stride, since prob­lems in night vision are a major factor in traffic fatalities. According to Consumer Reports, about 70 percent of accidents involving cars striking pedestrians occur at night.

Improved highway lighting, reflective paints on roads, and shoulder rumble strips, among other infrastructure initiatives, have all made night driving safer. Ironically, however, fog lights, high beams, and auxil­iary lights, all designed to increase safety, can put drivers of oncoming vehicles at risk because of increased glare from them.

Older people are especially susceptible to night vision problems—even if their daylight vision is okay—because of changes that occur in aging eyes, including a gradual reduction in the size of the pupil (so less light hits the retina) and a decrease in the number of rods in the retina (the cells that are important for twilight and night vision). There is also a loss in contrast sensitivity (the ability to distinguish an object from its background), which makes it harder to see pedestrians, animals, and obstacles on the road. Plus, the retina’s ability to quickly adjust between bright light (as with oncoming headlights) and low-light condi­tions decreases with age.

On top of these changes, older people are more likely to have other eye conditions that affect the ability to see in low light, including cataracts, macular degeneration, and glaucoma. Night vision may also worsen in people of all ages who have dia­betes or dry eye syndrome and after LASIK and other refractive eye surgeries.

Routine eye exams typically test vision only under daylight conditions, which does not predict night vision. In fact, many peo­ple test well in standard eye exams but have night vision problems, whether they are aware of them or not.

How low light affects vision

In a small study in the journal Optometry and Vision Science, researchers tested the visual acuity of 43 people (ages 14 to 32)—first at daylight levels and then at different levels of twilight—using light fil­ters and found that vision decreased significantly with each drop in illumination. In fact, the subjects, who had about 20/20 vision at daylight levels, dropped on average one to two lines on the eye chart in twilight conditions and almost three lines in dimmer light.

An older study, published in Human Factors, tested the driving performance of young, middle-aged, and older people under both day and night conditions. Participants in all age groups slowed their vehicles under low light conditions, but not enough to compensate for degraded visibility at night. And the middle-aged and older groups performed worse in spotting pedestrians.

Can food or supplements improve night vision?

Don't count on it. A Chinese study in Nutrition found that lutein supplements improved contrast and glare sensitivity, which suggests that this carotenoid, found in many fruits and vegetables, may improve twilight and night vision. But the findings may not generalize beyond a Chinese population—and it’s unlikely that Americans who are well nourished would benefit from eating bushels of carrots or other lutein-rich pro­duce. The only benefit would be in people who have deficiencies due to, for instance, malabsorption problems or alcoholism. Plus, we don’t recommend carotenoid supple­ments, which can have adverse effects.

What about blueberries, which are also purported to improve night vision? They did not have a clinically beneficial effect in a study in the Journal of Agricultural and Food Chemistry. Of course, it’s always a good idea to eat lots of colorful fruits and vegetables, which offer an array of vitamins, minerals, and phytochemicals and have other important health benefits.

What you can do

  • If you have trouble seeing in low light, consult an eye care professional, who, in addition to giving you a standard eye exam, may use special charts or other equipment to pinpoint any night vision problems. You may be a candidate for prescription night-driving glasses, even if you don’t wear glasses during the day. These other tips may also help:
  • Ask your eye care professional for glasses with anti-reflective coatings, which cut down on glare. High-definition lenses can give you sharper vision and also reduce glare for nighttime driving. Yellow-tinted lenses can increase contrast sensitivity, though they may also intensify glare, and any tint reduces the amount of light that reaches the eye.
  • If you are having cataract surgery, ask about getting an aspheric intraocular lens, a type of “premium” lens that improves con­trast sensitivity (though these lenses are not covered by Medicare or other insurance).
  • Treat dry eye syndrome if you have it (and get evaluated if you think you have it). The condition can cause you to experience light scatter. For more on dry eyes, see Dry Eyes: Treatment and Prevention.
  • When driving at night, make sure your headlights, windows, and mirrors are clean; use your window defoggers in inclement weather; slow your speed; and turn on the high-beams more often (but not in fog or when there are oncoming vehicles).
  • If you are in the market for a new car—and can afford the über-expensive price tag—check out models that have new night-vision systems, such as infrared cam­eras that detect people and animals and then alert you to their presence through an image on the dashboard or by beeping. Such high-tech features, available only on high-end luxury cars now, should become more common and affordable in the future.
  • Lastly, some tips for home owners, pedestrians, and cyclists: Problems with night vision are responsible for an untold number of falls, so you should keep your walkways well illuminated at night and not skimp on indoor lighting. Wear light-col­ored clothing or reflective markings if you are walking or cycling on dark streets.

Note: If you are over age 50 and want to participate in a research project on night vision being conducted at Queensland Uni­versity of Technology in Australia, take this online survey. It asks detailed questions about how well you see in low light and how this impacts your driving and other daily behav­iors. It takes about 15 minutes and is done anonymously; you get no personal feedback.

Also see Aging and Driving.