As the season of spring moves ever closer, and we find ourselves taking to the great outdoors more and more often, it is important to remember that our eyes deserve a ‘glance’ in the protection formula. Most of us know that using sun screen is vital to reducing risk for skin cancers, but are we giving the same consideration to our eyes, and the eyes of youngsters?
‘While preventing UV exposure is important at any age, damage is cumulative and can never be reversed, so it is vital to start preventing this harmful radiation exposure when young through the use of protective eyewear. Children are especially vulnerable to the sun’s damaging rays because the lenses of young eyes are clearer than those in mature eyes, allowing for more UV to penetrate and reach the back of the eyes. Even with this increased risk, more than one-third of parents (34 percent) report that children younger than 13 rarely or never wear shades.’ (www.thevisioncouncil.org)
According to Allaboutvision.com ‘Risks of eye damage from UV and HEV exposure change from day to day and depend on a number of factors, including:
Geographic location. UV levels are greater in tropical areas near the earth’s equator. The farther you are from the equator, the smaller your risk.
Altitude. UV levels are greater at higher altitudes.
Time of day. UV and HEV levels are greater when the sun is high in the sky, typically from 10 a.m. to 2 p.m.
Setting. UV and HEV levels are greater in wide open spaces, especially when highly reflective surfaces are present, like snow and sand.
In fact, UV exposure can nearly double when UV rays are reflected from the snow. UV exposure is less likely in urban settings, where tall buildings shade the streets.
Medications. Certain medications, such as tetracycline, sulfa drugs, birth control pills, diuretics and tranquilizers, can increase your body’s sensitivity to UV and HEV radiation.
Surprisingly, cloud cover doesn’t affect UV levels significantly. Risk of UV exposure can be quite high even on hazy or overcast days. This is because UV is invisible radiation, not visible light, and can penetrate clouds.’
High-energy visible (HEV) radiation, or blue light, is visible. Although HEV rays have longer wavelengths (400-500 nm) and lower energy than UV rays, they penetrate deeply into the eye and can cause retinal damage. Because the cornea appears to absorb 100 percent of UVB rays, this type of UV radiation is unlikely to cause cataracts and macular degeneration, which instead are linked to UVA exposure.
Ultraviolet (UV) rays are higher in energy and do not fall within the realm of visible light. In the electromagnetic spectrum, radio waves have the lowest energy, and gamma rays have the highest energy.
While many people refer to ultraviolet radiation as UV light, the term technically is incorrect because you cannot see UV rays.
The three categories of invisible high-energy UV rays are:
UVC rays. These are the highest-energy UV rays and potentially could be the most harmful to your eyes and skin. Fortunately, the atmosphere’s ozone layer blocks virtually all UVC rays. But this also means depletion of the ozone layer potentially could allow high-energy UVC rays to reach the earth’s surface and cause serious UV-related health problems. UVC rays have wavelengths of 100-280 nanometer (nm).
UVB rays. These have slightly longer wavelengths (280-315 nm) and lower energy than
UVC rays. These rays are filtered partially by the ozone layer, but some still reach the earth’s surface.
UVA rays. These are closer to visible light rays and have lower energy than UVB and
UVC rays. But UVA rays can pass through the cornea and reach the lens and retina inside the eye.
Overexposure to UVA radiation has been linked to the development of certain types of cataracts, and research suggests UVA rays may play a role in development of macular degeneration. The retina is a thin, light-sensitive layer of tissue that lines the inner surface of the eye. When light hits the retina, it sends off signals to the visual centres in the brain. Some studies have shown an association between sun exposure and damage to the macula (central part of the retina) known as macular degeneration, a common cause of blindness in people over age 50 years.
UVB rays are thought to help cause pingueculae and pterygia. These growths on the eye’s surface can become unsightly and cause corneal problems as well as distorted vision. In high, short-term doses, UVB rays also can cause photokeratitis, a painful inflammation of the cornea. “Snow blindness” is the common term for severe photokeratitis, which causes temporary vision loss usually lasting 24-48 hours.
Environment and Climate Change Canada says ‘In the late winter and early spring, fresh white snow can increase the amount of Ultraviolet (UV) radiation you receive by up to 85 per cent. Protect yourself on the ski slopes or on the trails by wearing sunscreen on your face, and sunglasses to protect your eyes. To best protect your eyes from the sun’s harmful UV and HEV rays, always wear good quality sunglasses when you are outdoors.’ (www.ec.gc.ca)
Ice Fishing would also be considered an important time to remember your sunglasses. Reflected UV light is just as damaging as direct UV. For example, water reflects up to 100% UV light, Snow reflects up to 85% UV, Dry sand and concrete reflect up to 25% UV and Grass reflects up to 3% UV light.
To protect your eyes from harmful solar radiation, sunglasses should block 100 percent of UV rays and also absorb most HEV rays. Frames with a close-fitting wraparound style provide the best protection because they limit how much stray sunlight reaches your eyes from above and beyond the periphery of your sunglass lenses. While the eyes have their own built-in protective mechanisms (eyelids, lens, cornea), these only offer partial coverage so sunglasses are essential.
An optician can help you choose the best sunglass lenses for your needs. The Vision Council has released a 2015 report on UV protection, called Protection for the Naked Eye: Sunglasses as a Health Necessity. (www.allaboutvision.com)
For an up-to-date UV Index search: http://weather.gc.ca/.