For most people, a low-cost pair of sunglasses with UVB and UVA protection will do the job.
Follow these safety tips when choosing sunglasses to reduce your risk:
- Choose close-fitting wrap around eyewear. Close-fitting or wrap-around sunglasses helps to prevent stray light from entering from the sides.
- Choose dark lenses. Make sure the lenses are dark enough to keep your eyes comfortable, but not so dark that they reduce your vision.
- Reduce glare. If you spend a lot of time outdoors
with intense glare from sunlight bouncing off snow or water, you should
wear sunglasses that block blue light. Medium to dark lenses with a
grey, or slightly brown or green tint, will filter out most blue light.
- Choose scratch-resistant coatings. Most sunglasses
have plastic lenses. These lenses are tougher than glass and less likely
to shatter. If you buy plastic lenses, look for a pair with a
scratch-resistant coating.
- Check for distortion. Check the lenses for
distortion by putting the sunglasses on and looking at a rectangular
pattern, such as floor tiles. If the lines stay straight when you move
your head up and down, and side-to-side, then the amount of distortion
is acceptable.
- Get enough UV protection. You cannot tell how much
UV protection a pair of sunglasses will provide by their price, colour,
or by the darkness of the lenses. Look for a label with UVB and UVA
protection.
Manufacturers follow voluntary industry standards when
labelling sunglasses. Sunglasses that comply with industry standards for
UV protection are grouped in three categories:
- Cosmetic sunglasses have lightly tinted lenses for
use in sunlight that is not harsh. They block up to 60 percent of
visible light and UVA rays, and between 87.5 and 95 percent of UVB rays.
These glasses are not usually recommended for daylight driving.
- General purpose sunglasses block from 60 to 92
percent of visible light and UVA rays, and between 95 and 99 percent of
UVB rays. These sunglasses are good for driving, and are recommended
whenever sunlight is harsh enough to make you squint.
- Special purpose sunglasses block up to 97 percent
of visible light and up to 98.5 percent of UVA rays. They also block at
least 99 percent of UVB rays, and are suitable for prolonged sun
exposure. These sunglasses are not recommended for driving.
- Contact lenses, even those with UV protection, does not provide full coverage for the eyes and the skin around the eyes.
Sunglasses are made with different kinds of lenses to meet different needs:
- Regular lenses reduce the brightness of everything evenly.
- Polarizing lenses are designed to cut glare due to
reflection. This means they are good for driving and outdoor activities
in the snow or on water.
- Photochromic lenses change with the intensity of
UV light by turning darker when outdoors and lighter when indoors. If
you wear these for driving, choose sunglasses that are fairly dark.
- "Flash" or mirror lenses reflect all or part of
the light instead of absorbing it. They offer no performance advantage
because they scratch easily. You should choose a pair with a
scratch-resistant coating.
The sun produces many different kinds of energy. The kinds most likely to injure the eye are:
- ultraviolet radiation, which is invisible and is often called "UV rays"
- bright or intense light
- blue light
UV rays carry more energy than visible light rays,
so the eye is at greater risk of damage from absorbing UV rays than from
absorbing other kinds of light. There are two types of UV rays that
reach the Earth's surface: UVA and UVB. These rays can cause, or speed
up the progress of, several diseases that affect the eye or its
supporting structures. UVB rays have also been linked to
skin cancer.
Most of the damage caused to eyes by UVB and UVA rays happens over a
long period of time and cannot be reversed. Sensitivity to UV rays
varies from one person to the next.
Blue light is visible light in the blue portion of
the colour spectrum. The intense glare of light reflecting off snow or
water contains blue light. Your eyes cannot focus clearly in blue light.
Some scientists believe that routine exposure to blue light over many
years may age the retina and increase the risk of blindness in some
people over the age of sixty.
When your eyes absorb ultraviolet radiation and visible
light from the sun, heat or chemicals react in eye tissue. These
reactions can cause permanent damage if the eye's natural ability to
heal itself is overwhelmed.
Different parts of the eye absorb different kinds of
UV rays and visible light. For example:
- The surface layers of the outer part of the eyeball (the cornea and the conjunctiva) absorb UVB rays.
- The lens absorbs mainly UVA rays.
- The retina (the light-sensitive lining at the back of the inner eyeball) absorbs visible light.
If eyes are overexposed to UV radiation, the front portion of
the eyes can be damaged. If visible light is too bright or intense, or
if you stare directly at the sun, even briefly, the retina can be
damaged, causing permanent loss of vision. UV radiation, along with wind
and drying of the eye, may cause snow blindness, an uncomfortable but
temporary condition.
There is some evidence that daily exposure
to UV radiation in very bright sunlight over many years may increase the
risk of developing cataracts.
Cataracts cause a gradual clouding of the natural lens of the eye.
Thank you
Health Canada!