Friday, January 30, 2009

Decreased Daylight during Winter affecting your driving?

With shorter daylight hours during the winter months, many of us are forced to drive at night. Many Americans experience difficulty driving at night or in the evening hours.

Actual night blindness is atypical. Night blindness can be caused by alcoholism, diseases of the liver, long-term vitamin A deficiency, chronic starvation, and deficient fat absorption. Ocular conditions that may cause night blindness are glaucoma, drug toxicities and some hereditary disorders. A condition that may mimic night blindness is night myopia, which may also reduce night vision. Considerable variability among people exists in retinal sensitivity to light. Additionally, as people age, night vision diminishes.

Studies have shown that as little as two to three hours of bright sunlight exposure can delay the onset of dark adaptation, resulting in a delay of full night vision sensitivity for hours. After 10 consecutive days of sunlight exposure, losses in night vision can be as great as 50% loss in visual acuity, visibility range, and contrast discrimination.

Here are some recommendations to protect your eyes during the day and conserve night vision. When possible, remain inside during the day of night driving. While outside, residents should wear dark sunglasses and a hat with a brim, which blocks a considerable amount of solar radiation. Polarized sunglasses that reduce visible light transmision will help prevent degradation of night vision. However, in some people, it may take days to weeks to recover full night vision.

For sunglasses to be effective, the rays of light need to be focused in the eye. Thus, colored visors or spectacles are not always protective during the day. To best protect night vision, while providing good comfort and contrast, dark sunglasses with a neutral gray tint are recommended during the day. Heavily tinted sunglasses that are too dark, may actually reduce visual acuity, especially on cloudy days. Lighter sunglasses may not fully protect your night vision either. Therefore, optometrists generally recommend using polarized sunglasses on sunny days.

One product that pertains to this article is the Night Driving Glasses by Tag Heuer. First off, these should not be confused with thermal night vision. Thermal night vision is commonly seen in action movies, where a few elite or covert special ops take down a bunch of gangsters or thugs. The Dark Knight, aka Batman also employs thermal night vision, plus some other technology to be developed in the future. These glasses were originally inspired and developed for the internationally renowned 24 Hours of LeMans sports car endurance race. These are the same glasses you see on Formula One racer Sebastien Bourdais and Indianapolis 500 driver Sarah Fisher. Tag Heuer has made these glasses available to the general public. These glasses have been optimized for driving at night, by correcting low-light and short-sightedness situations that oftentimes occurs when driving in the dark. This article should not be substituted for medical advice, as always, seek assistance from a profession eye care specialists.


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