Sunglasses are an important industry and wearing sunglasses is not just about making a fashion statement. There is plenty of evidence that your eyes need protection from damaging light rays. While we may enjoy the Sun’s warm infrared rays, its ultraviolet light, invisible and unnoticeable, is more sinister.
The total amount of UV light we are exposed to and absorb is affected by how high we are relative to sea level, how much time we spend outdoors. And while UV light can hit our eyes in a straight line, it also gets reflected on the ground and reaches us from below and from the sides.
An impressive number of eye diseases correlate with exposure to UV light, from pre-cancerous growths on the eyelid to snow blindness to conditions affecting the back of the eye. A child’s eye is particularly sensitive to UV exposure. The lens inside their eye is still clear and their pupil is wider. This means that 2 to 5% of the UV rays received by their eyes can actually reach the retina at the back.
And there’s blue light. Between green-colored light and ultraviolet light, there’s a high-energy region of the visible spectrum that has been implicated in a common form of age-related blindness.
So, we need to protect our eyes from high-energy rays of light. How do we do that?
Casting light on sunglasses
UV protection: Glasses advertising “UV 400” will block essentially all UV rays. This is in reference to the wavelength 400 nanometers. The UV protection itself does not diminish over time, even though the tint of the lenses could fade.
Price: While you may think that the more expensive a pair of shades is, the better the UV protection is, that is simply (and thankfully) not true. A recent study published in the Canadian Journal of Ophthalmology looked at over 200 pairs of sunglasses on sale in Quebec City in three price ranges and tested them to see if they met the standards for filtering out harmful UVs. While there are no mandatory standards in Canada, the researchers used the four existing standards in the world: United States, European Union, Australia, and New Zealand. All tested sunglasses above the 21$ price point met these standards, and almost all of the cheaper sunglasses did as well. Price had clearly no real bearing on their ability to filter out UV light, but it did have a role to play on the clarity of the visible light they transmitted.
Tint: The color of the lenses, including how dark they are, has no bearing on the UV protection. It boils down to preference. “If you want brighter colors, you go for the brownish, pinkish tint, like the old Serengeti lens,” Careau says. I agree from personal experience. My own regular prescription eyeglasses are tinted toward red, and the colors really pop. Some people prefer grey lenses, which Careau tells me lead to a “faded, dim, dark” look without altering colors. As for really dark tints, they simply block more visible light. If your eyes are more sensitive to light, you may want to avoid lighter tints. Orange and yellow lenses offer better contrast, which is useful to tennis players, though they obviously distort colors.
Polarized: While this feature has no impact on UV filtration, it will cut down on glare coming from horizontal surfaces, like snow or the surface of a lake. But if you’re a pilot, watch out! Polarized lenses may interfere with your ability to read instruments that have an anti-glare coating and with LCD readouts, as well as reduce visibility. Hydroplane pilots in particular will have difficulty judging distances for landing while wearing polarized lenses. For everyone else? “It’s like having air conditioning in the car,” Careau suggests. “Once you’ve had it, it’s always more comfortable.”
Photochromic (AKA transition lenses): The idea of lenses that automatically get darker when go outside is very tempting but be warned. The technology behind them is triggered by UV light. Inside a car, where the UV light is being partially blocked by the windshield, your sunglasses probably won’t darken (although some more recent technology can partly get around that). Also, the transition is not consistent across temperatures. When its colder, transition lenses tend to get much darker than when it’s warm, Careau tells me.
Wraparound: Because UV light can bounce around, it can reach your eyes from the side. Wraparound sunglasses thus offer better protection.
Raising a glass to sunglasses
To protect our eyes from the Sun, we should seek out sunglasses that block 99-100% of UVA and UVB rays and we should favor wraparounds. The color does not matter when it comes to blocking harmful rays, and while polarized lenses cut glare, the polarization does not improve the blocking of UV rays.
As for the weather, clouds make no difference: UV light goes through them. And winter is no excuse to leave the shades behind, as the snow reflects 94% of the UV rays it receives.
Sunglasses and UV Protection
But even with the best shades gracing our faces, we should not forget sunscreen and a hat. While lenses can fully block UV light, wearing sunglasses does not. Light can get reflected and enter our eyes from above, below, and from the sides.
As for my buck-fifty pair of shades, it’s not bad. I won’t be trading in my more expensive wraparounds any time soon, but these cheap alternatives do what it says on the tin. No reason to throw shade at them.