Seeing the light

June 1, 2005
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Sure, workers may want to wear sunglasses for comfort, but they may need them for protection.

The eyes are susceptible to being burned by the sun(1). The cornea, lens and retina are all vulnerable to overexposure to ultraviolet (UV) rays. Over time these UV rays — invisible to the human eye — can harm the eye if left unprotected. So workers who are heavily exposed to sunlight should protect their eyes with UV-blocking sunglasses.

Why wear sunglasses?

Sunglasses have several important purposes for workers:

Increase comfort — Sunglasses reduce glare and brightness, whether from the sun directly or from water or other shiny or reflective surfaces. Glare can be painful and dangerously distracting while working.

To ensure that sunglasses will block glare, lenses should be dark enough to hide your eyes. For comfortable vision on sunny days, sunglasses should block 75 percent to 90 percent of visible light(1).

Improve visibility — Particularly for drivers, sun glare can be a dangerous problem. Many drivers find themselves temporarily blinded as they are driving directly into the glare of the sun. Certain road conditions can raise the amount of UV that drivers are exposed to by up to 85 percent(2).

Sunglasses improve vision by enhancing contrast. Things appear more vivid and sharp.

Protect the eyes — Sunglasses filter light and protect the eyes from UV rays. Mounting evidence shows that exposure to UV rays can damage eyes(3). These invisible rays can lead to such eye diseases as cataracts, macular degeneration and photokeratitis (“sunburn” of the eyes that can take up to a week to heal)(4).

Symptoms of UV overexposure to the eyes include(5):

  • a burning and painful sensation in the eye;
  • a sensitivity to light;
  • the sensation of a foreign object in the eye, sometimes described as sand in the eye;
  • tearing.

Glasses can be treated to filter out UV rays. Sunglasses that are not treated for UV light may actually be detrimental to the eyes. Dark lenses reduce light entering the eye, causing the pupil to dilate and exposing the inside of the eye to more UV radiation than without the sunglasses(1).

Your workers should be equipped with sunglasses that filter out 99 percent to 100 percent of UV rays. Anyone who spends a lot of time outdoors should be cautious about UV radiation.

Lens characteristics

Keep in mind that the shade and color of sunglass lenses have no effect on the glasses’ ability to block UV light — UV coating is a separate treatment.

Polarized lenses, ideal for sunny conditions and for driving, are excellent at blocking glare. Polarized filters are added to the lenses during the manufacturing process. Polarization does not block UV light, although lenses may be treated for this as well.

Photochromic lenses are sensitive to light, quickly darkening when exposed to bright light. These lenses enable users to avoid having to switch between prescription glasses and sunglasses when going in and out of the sun.

References

(1) VisionWeb web site, an independent company servicing the eye care industry, www.visionweb.com

(2) “Health News — Eye Protection,” AAA World, May/June 2005, p.34

(3) Prevent Blindness America web site, a volunteer eye health and safety organization, http://preventblindness.org

(4) Vision Council of America web site, optical trade association, www.visionsite.org

(5) Princeton University Environmental Health & Safety web site, http://web.princeton.edu/sites/ehs

SIDEBAR: Choose your color wisely

Different lens tints filter different wavelengths of light. Some may enhance or distort colors and affect contrast. Select your tint based on your need.

  • Gray — Allows true color perception, but does not enhance contrast; good for cycling or running.

  • Green — Allows true color perception and good contrast in bright light; reduces eye strain in bright light.

  • Brown — Good in hazy sun, enhances contrast; good for high-glare environments.

  • Amber — Brightens cloudy, hazy or foggy skies; excellent for contrast; minimizes eye strain; distorts color (images look yellow-orange).

  • Yellow — Improves contrast and depth perception in low light; good for overcast days.

  • Red — Excellent depth perception in low light; contrasts objects against blue or green backgrounds.

  • Mirrored — Reflects high-intensity light to reduce glare; available in various colors.
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