Seeing the light

Seems the sun doesn't only cause skin cancer, it also wreaks havoc with eyes not protected by sunglasses.

Cataracts, retinal and corneal injury, a growth on the white of the eye called pterygium, even macular degeneration -a leading cause of vision loss in older people -can result from or be aggravated by over-exposure to the sun's ultraviolet (UV) and visible rays, says Dr. Mark Pogue, an Ottawa optometrist.

Damage from the two types of UV rays, UVA and UVB, is considered more dangerous than that from visible rays, which typically cause temporary conditions like snow blindness. These visible rays are sometimes called blue light because they are in the blue portion of the colour spectrum.

Corneal damage caused by blue light reflecting off snow or water usually heals by itself, says Pogue, although prolonged exposure may age the retina and even increase the risk of blindness, according to some experts. Surgery can often correct pterygium and cataracts, but other conditions caused by UV rays are not reversible.

There are no reliable studies showing a population-wide increase in eye damage from the sun, Pogue adds, but anecdotal evidence for it seems to exist.

The damage, according to Health Canada (http: //hc-sc.gc.ca/hl-vs/ iyh-vsv/prod/glasses-lunetteseng.php), occurs when the eyes absorb light, which is a form of energy. That energy causes heat or chemical reactions in eye tissue. If the eye's natural ability to heal itself is overwhelmed by too much energy, longterm injury results.

Pogue says that wearing sunglasses from a young age can help prevent the havoc, which may take decades before making itself known. However, telling some young people to protect their eyes is "like when your mother tells you to eat your vegetables because some day you'll be glad you did. You hear but you don't listen."

WHAT TO LOOK FOR WHEN BUYING SUNGLASSES

UV Protection

Get glasses that protect against both UVA and UVB rays. Different parts of the eye can be damaged by each type of ray.

The Health Canada website explains that voluntary industry standards rate sunglasses as cosmetic, general purpose and special purpose depending on their UV protection.

General purpose glasses, for example, block 60 to 92 per cent of visible light and UVA rays, and 95 to 99 per cent of UVB rays. Wear them when you are driving or whenever sunlight is so harsh that you have to squint.

Sunglasses labelled UV400 block most harmful UV rays.

Blue Light Protection Medium to dark lenses with a grey, slightly brown or green tint filter out most blue light, according to Health Canada.

Polarizing Lenses Good for cutting glare from reflection. Use for skiing, boating and driving.

Photochromic or Transition Lenses

These change with the intensity of the UV rays, turning darker outdoors and lighter indoors. Sheldon Feinberg, an optician with Laurier Optical at Place d'Orléans, says not to buy these glasses for driving: car windows stop some UV rays and reduce the effectiveness of the glasses.

Gradient Lenses These lenses, which are darker on top than on the bottom, look sexy but are "just for style unless they're UV-coated," says Feinberg. He also cautions that dollar-store sunglasses, even if fully UVprotected, can cause eye strain because the lenses are not usually precision ground.

Mirror Lenses These reflect all light rather than absorbing it and help cut glare, but often scratch easily.

Other Precautions An informative YouTube video about UV rays posted on Pogue's website (orleans-optometry.com) suggests buying sunglasses that fit closely to the face to protect against stray rays entering from the sides and top.

The same video, by Halifax optometrist Dr. Toby Mandelman, says that most contact lenses provide some but not total UV protection.

Price and protection don't necessarily equate, although if you buy your sunglasses from an optician -usually a more expensive proposition -you will be getting the advice of an expert.

Other tips Avoid the summer sun when its rays are strongest between 11 a.m. and 4 p.m. A broad-brimmed hat or visor gives added protection to your eyes.