ARTICLE BY: Dr. John Astles

By far the greatest source of ultraviolet (UV) light exposure, that we will experience in our lives, is the sun. Therefore, as warmer weather approaches, it is important to know both why the eyes need to be protected from UV light and how this is best accomplished. Ultraviolet light is made up of UVA, UVA and UVC. We only have to worry about the first two since UVC is blocked by the ozone layer of the atmosphere before reaching us. UVB is absorbed by the cornea -the front surface of the eye. Not only does it cause skin tanning (and burning), it can cause an inflammation of the cornea called photokeratitis. (In the winter weather this is known as snow blindness.) As for UVA, some of it can pass through the cornea to the lens and retina. Thus overexposure can be associated with the development cataract and may increase the risk of macular degeneration. (This is the leading cause of blindness in adults over age 55 in Norh America.)

What should you do to protect yourself? The main thing you can do, especially if you spend much time outdoors, is to wear sunglasses. There are many choices and lens types but one aspect should be a constant. They should block 100% of the UV light. Hats are helpful and, of course, do not forget sunscreen.

There is a wide assortment of sun lens choices depending on individual needs. If you spend time near the water, such as with fishing, boating or the beach, sunglasses with polarized lenses would be a good idea. This is because they take away the glare coming off the water and allow for truer, clearer, more comfortable vision. Antireflection coatings on the lenses are useful to further reduce glare and improve vision. (Some more advanced coatings are designed to block UV light from being reflected into the eye from the back surface of the lens.) For driving, polarized lenses are again a good idea to block glare coming off the vehicle hood. As to lens tint colour, brown arguably provides some enhancement to the vision while driving and grey affectively reduces light intensity evenly without altering colour perception. Photochromic lenses, ones that actively darken in response to light, are not always a good substitute to proper driving sunglasses since they generally do not darken sufficiently when behind the windshield of a car.

The use of proper sun wear, not only makes for better more comfortable vision, but helps reduce the risk for the development of some vision compromising eye diseases. If you have concerns as to what is most appropriate for you, the doctors and staff and East London Optometry would be delighted to assist.

John Astles O.D. is the founding optometrist at London Ontario’s East London Optometry.