August 24, 2009
Summer's almost over and you've probably spent plenty (but can there ever be enough?) time outdoors enjoying the sunshine. And hopefully you've been sporting appropriate sun protection while doing it. No, not just the coconut-scented SPF 30 you've no doubt been slathering on at the beach, we're talking about sunglasses! That's right, beyond making you look cool, wearing the right pair of shades is crucial to lifelong eye care.
Did you know? Most of the sun damage to eyes occurs gradually over a long period of time and is irreversible, making it important to protect them at all stages of life.
Sunglasses are available in all manner of colors and styles and can range in cost from $5 at the flea market to$400 (or more!) for the designer duds. But if fashion style and cost are not what determines the effectiveness of sunglasses, then what does?
There are a few key things that sunglasses should do, regardless of their cost. First, they should block out ultraviolet radiation (UV) from the sun. UV rays are invisible and can be divided into two groups: UVA rays pass through glass, water, clouds and most clothing and are linked to early wrinkling and cataracts (a clouding of the natural lens of the eye) while UVB rays are the more dangerous "burning" rays associated with sunburn, cancer and photokeratitis (sunburn of the eye). Look for glasses that "block" or "absorb" 99-100% of UVA and UVB radiation.
Did you know?
You can't tell how much UV protection a pair of sunglasses offers from its price, or the colour and darkness of its lenses. Look for glasses labelled with the type (UVA or UVB) and amount of protection.
The second thing sunglasses should do is protect your eyes from intense visible light, such as bright sunlight. This is important since looking at intense light can damage the retina at the back wall of the eye, leading to a permanent loss of vision.Choosing darker glasses is a good idea for outdoor sports (like hiking and skiing) where you're exposed to bright light for long durations,while slightly lighter glasses are better for driving. Wrap-around styles of sunglasses can reduce the intensity of light coming in from the sides.
Did You Know?
While invisible UV light damages mostly the outer surface and lens of the eye to cause cataracts, bright visible light is absorbed mostly by the retina, which can become permanently scarred.
Lastly,sunglasses should reduce glare associated with reflected light (e.g.off of water or snow). Reducing glare is important during activities such as driving, to improve contrast and visibility by cutting out distortive reflections. The level of protection from glare depends on the darkness of the glasses and whether they are polarized.
So now that you know what sunglasses should do, how do you go about choosing the right pair? There are several types of lenses you can choose from, each with its own pros and cons. Glass lenses are heavier and costlier, but also more durable and scratch resistant than the lighter plastic lenses. With either glass or plastic, regular lenses reduce the brightness of everything while polarizing lenses also reduce glare. Photochromic lenses (better known by the trade name Transitions®) darken with increasing light intensity to provide scaled protection when moving between the indoors and outdoors.
While the type of sunglasses you buy will depend on your personal preferences for the type of lens and the frame style (regular or wrap-around), the important thing you shouldn't forget is to look for lenses with 99-100%UV blockage and good protection from intense light. Even when you're rocking you cool shades, don't forget that 100% UV blockage doesn't include the light that can get in around the sides of your glasses and that the risk of sun damage is greatest between 10 am and 2 pm. Also,while summer's almost at an end, bright sunlight and UV rays are found all year, so you should wear your sunglasses year-round, too.
Health Canada — It's your health: Sunglasses
Health Canada — It's your health: Ultraviolet radiation from the sun
HowStuffWorks: How Sunglasses Work
CBC News In Depth: Sunglasses — Don't be left in the light
May Cheng studies the properties of cardiac potassium channels(proteins that help regulate your heartbeat) as part of her PhDtraining at the University of British Columbia. She also received herMaster’s and Bachelor’s degrees from UBC. When she’s not in the lab,she’s probably dreaming up her next culinary adventure.