Frequency of Examination
Sunglasses – Required Equipment for Outdoor Living
Are you an outdoor enthusiast? Do you get excited about skiing as the snow starts to cover the ground? Does your pulse quicken at the prospects of getting that new mountain bike on the back-trails? Do you enjoy long walks in the sunshine? As the excitement builds and you check over your equipment, take a minute to think about proper eyewear.
Sunglasses are worn for three reasons. Bright light and glare cause the eyes to squint and water, so sunglass wear enables comfortable vision. Protection from ultraviolet (UV) light radiation can prevent short-term effects like photokeratitis (snow-blindness), and long-term effects like early cataracts. Sunglasses also maintain dark adaptation, allowing quick transition to night-time or indoor lighting conditions when removed.
Of the three reasons, protection from ultraviolet exposure is of particular concern due to its potential for damage to the eyes. Life-time cumulative exposure to UV radiation is a factor in the development of cataracts and age-related macular degeneration. With the ozone layer depleting, UV levels are at an all-time high. Add increased life-expectancy to the mix, and it becomes more important to protect yourself now.
Children are especially important. They spend more time outdoors than adults, and their transparent young eyes allow more UV rays inside. They live at a time when ozone loss and increased UV radiation is greater than ever. And they can expect to need their eyes for a longer time than their parents or grandparents. Since they get a majority of their life-time exposure before adult-hood, early protection now will better their chances of avoiding eye health problems later in life.
Skiers should be especially concerned. Most UV exposure is reflected into the eyes, rather than direct sun-to-eye transmission. New-fallen snow is about 75% reflective (grass is about 3-5%, water about 7-10%), so skiing provides one of the highest amounts of UV exposure (ever wonder why new-fallen snow is so bright?). Cloudy, bright days also require sunglasses, since clouds do not block UV radiation and there is no infra-red radiation (heat) like there is on clear, sunny days to alert you. Those who also enjoy downhill skiing increase their exposure, since the added elevation puts them closer to the radiation source. Exposure is greatest between 10 AM and 2 PM (72% of the total UV radiation daily).
Some tips to follow when selecting non-prescription sunglasses:
Select sunglasses that block 99-100% of both UVA and UVB. Price is not an indication of protection. Check labels closely.
Try the sunglasses on while looking in a mirror. If you can see your eyes easily through the lenses, they probably aren’t dark enough to ensure visual comfort. Lenses that screen 75-90% of visible light are best.
Gray is a good choice of lens color, since it does not modify how you see the color of your surroundings. Green and brown are also acceptable choices.
Check that the tint is uniform between the two lenses. You don’t want one lens darker than the other. More than a 10% difference may affect your depth perception.
Look for distortions in the lens by holding them at arms length and looking through them at a straight line (such as the edge of a door) in the distance. Slowly move the lens across the line. If the straight edge distorts, sways, curves or moves, try another pair of sunglasses.
Polycarbonate lenses are the most impact resistant today. These would be useful for active children.
Large aperture frames offer better coverage for UV protection than the small frames so common today (although small frames steam up less due to better ventilation around the lenses). Wrap-around sunglasses can provide additional UV protection. For those who have to wear prescription glasses, don’t despair. Wearing clear plastic lenses affords significantly more UV protection than no glasses, and there are more options available today than ever before: Tinting an old pair of glasses into sunglasses with a UV blocker coating is inexpensive.
Plastic photochromic lenses (Transitions or Colormatic) are growing rapidly in use, and relegating the older, heavier glass photochromics to the sidelines. These have the ability to change with various lighting conditions, but still maintain the UV protection.
Many frame manufacturers are making sunglass clips which attach to the frame in a way that prevents scratching the lenses. Clips can even be custom-made for your new eyewear. Older-style clips attach to (and may potentially scratch) the lenses.
Solar shields are available which completely cover and enclose the frame.
Wearing contact lenses, or having refractive surgery, puts you back into the non-prescription section above.
For additional questions not covered here, send an e-mail to the NBAO in the “Contact Us” section. Hope you have a great outdoor season!
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