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The court is reflected in the sunglasses of a spectator watching the action.Jason Cairnduff/Reuters

THE QUESTION: Summertime is finally here and I want to get a new pair of sunglasses. What should I buy to best protect my eyes?

THE ANSWER: There is certainly good reason to guard your eyes against the sun. But it can be a challenge finding a reliable pair of sunglasses that protect you from damaging rays, because the companies that make them are self-regulated.

The first thing you need to know is that eyes are extremely vulnerable to sunlight – particularly a form of solar rays called ultraviolet (UV) radiation.

UV rays are invisible, but they carry a lot of energy. They can speed up the natural aging process of the eyes and contribute to several sight-limiting conditions, including cataracts, a clouding of the lens of the eye. Eventually, vision can become so impaired that the natural lens may need to be replaced with an artificial lens.

Another concern is visible light in the blue portion of the colour spectrum. Studies suggest that blue light may accelerate or worsen a form of vision loss called age-related macular degeneration.

When you're picking sunglasses, you will want to find a pair that shields against both UV rays and blue light, says Harmeet Gill, an ophthalmologist at Sunnybrook Health Sciences Centre and Mount Sinai Hospital in Toronto.

Medium-to-dark lenses with a grey or a slightly brown or green tint will filter out most of the blue light, according to Health Canada's website.

However, there is no way you can tell if sunglasses guard against UV light simply by their appearance. Companies will usually display labels stating that their sunglasses have a special coating that blocks UV rays.

Here's the catch: Companies in Canada are following voluntary industry standards for UV protection and no independent agency is actually checking if the claims are accurate, says Samuel Markowitz, a professor in the department of ophthalmology at the University of Toronto.

"As it stands now, it is basically self-declared compliance," he says. In other words, consumers can't be certain they're getting what is stated on the label.

Marie-France Faucher, a federal government spokesperson, said in an e-mail that companies are prohibited under Canada's Competition Act from making false claims. She adds that the Competition Bureau would investigate "all allegations of false or misleading representation."

Another government spokesperson, André Gagnon, said in an e-mail that "Health Canada is not aware of any health or safety issues relating to non-prescription sunglasses." Nor has it received any reports of problems.

So, without any formal complaints, there are no investigations. What's more, "there are no plans to introduce mandatory requirements for this product category," Gagnon notes.

In some other countries that also rely on voluntary industry compliance, random checks have found a significant portion of sunglasses incorrectly labelled, promising UV protection when it is absent.

Markowitz suggests that Canadians should "buy from a reputable company." What's a reputable company? "One that probably has large market share and has been around for years and has a reputable public track record. Try to avoid unknown suppliers," he says.

Still, the customer is relying on trust. To eliminate the uncertainty, Markowitz says, you could order a custom-made pair from an eyeglasses supplier, stipulating that you want a UV block. You could also request shatter-resistant, optical-quality lenses for added protection and clarity of vision.

Buying custom-made sunglasses may seem overly cautious. But in a system that relies on voluntary compliance, it's one way to boost your chances of getting a product that will properly protect your eyes.

Gill adds that the best protection is provided by close-fitting, wrap-around sunglasses that also block sunlight from the sides. Wearing a wide-brimmed hat also helps to keep the sun out of the eyes.

He adds that it's important to keep in mind that the eyes require a longer period of protection than the skin.

The sun causes the most harm to the skin – increasing the risk of skin cancer – when it's overhead, from 11 a.m. to 3 p.m. between April and September in Canada. At those times, the sun's rays travel through less atmosphere, making them especially intense.

But the sun poses a significant risk to the eyes even when it's low in the sky. In fact, the lower angle gives the sun's rays a direct pathway into the eyeball. Think of how hard it is to drive on the highway when you're heading into the rising or setting sun.

Furthermore, UV rays can penetrate clouds and reflect off surfaces such as snow, sand and water.

"To protect your eyes, you should be wearing sunglasses, day-long, year-round and even when it's cloudy," Gill says. "I know it sounds a bit crazy, but that's what the research actually shows."

Paul Taylor is a Patient Navigation Advisor at Sunnybrook Health Sciences Centre. He is a former Health Editor of The Globe and Mail. You can find him on Twitter @epaultaylor and online at Sunnybrook's Your Health Matters.