Sunglasses have been popular with people for years, both for comfort and as a fashion accessory. Eye Care Professional now believe there is another reason to wear sunglasses — to protect the long-term health of your eyes. Results from a dozen studies over the last 10 years suggest that long hours in the sun without proper eye protection increase your chances of developing eye disease.
In 1988, a group of Eye Care Professional studied 838 Chesapeake Bay fishermen who had spent years working on the water. The fishermen who wore no eye protection had three times as many cataracts as those who wore sunglasses or a brimmed hat. A cataract is a clouding of the eye's natural lens. Based on this study and others, Eye Care Professional now recommend that you wear UV-absorbent sunglasses and a brimmed hat whenever you're in the sun long enough to get a suntan or a sunburn, especially if you live at a high elevation or near the equator.
Conflicting Claims
Manufacturers have developed new sunglasses designed to protect eyes from the sun's harmful effects. They promise protection from ultraviolet light and other kinds of natural radiation. It is more important to protect your eyes from some kinds of light than others.
"Blocks
99% of ultraviolet rays"
You should always buy sunglasses with this feature. Long-term exposure to
ultraviolet (UV) radiation in sunlight is linked to eye disease. Both plastic
and glass lenses absorb some UV light, but UV absorption can be improved by
adding chemicals to the lens material during manufacturing or by applying
special lens coatings. Shop for sunglasses that block 99 or 100% of all UV
light. Some manufacturers' labels say "UV absorption up to 400nm."
This is the same thing as 100% UV absorption.
"Blocks
90% of infrared rays"
Infrared wavelengths are invisible (they are longer than light rays that you
can see) and produce heat. Sunlight has low levels of infrared rays, and the
eye tolerates infrared well. Some sunglasses manufacturers make health claims
for their products based on infrared protection, but research has not shown
a close connection between eye disease and infrared rays.
"Blue-blocking"
Whether blue light is harmful to the eye is still controversial. Lenses that
block all blue light are usually amber and make your surroundings look yellow
or orange. The tint supposedly makes distant objects appear more distinct,
especially in snow or haze. For this reason, amber sunglasses are popular
among skiers, hunters, boaters and pilots.
"Polarized"
Polarized lenses cut reflected glare — sunlight that bounces off smooth
surfaces like pavement or water. They can be particularly useful for driving
and fishing. Polarization has nothing to do with UV light absorption, but
many polarized lenses are now combined with a UV-blocking substance. Check
the label to make sure the lenses provide maximum UV protection.
"Mirror-coated"
Mirror finishes are thin layers of various metallic coatings on an ordinary
lens. Although they do reduce the amount of visible light entering your eyes,
do not assume they will fully protect you against UV radiation.
"Wraparound"
Wraparound glasses are shaped to keep light from shining around the frames
and into your eyes. Studies have shown that enough UV rays enter around ordinary
eyeglass frames to reduce the benefits of protective lenses. Large-framed
wraparound sunglasses can protect your eyes from all angles.
"Gradient"
Gradient lenses are permanently shaded from top to bottom or from top and
bottom toward the middle. Single-gradient lenses (dark on top and lighter
on the bottom) can cut glare from the sky but allow you to see clearly below.
They are useful for driving because they don't dim your view of the dashboard.
But they're not as good on snow or at the beach, especially if they're clear
on the bottom. Double-gradient lenses (dark on top and bottom and lighter
in the middle) may be better for sports where light reflects up off the water
or snow, such as sailing or skiing. Double-gradient lenses are not recommended
for driving, because they make the dashboard appear dim.
"Photochromic"
A photochromic glass lens automatically darkens in bright light and becomes
lighter in low light. Most of the darkening takes place in about half a minute,
while the lightening takes about five minutes. They come in a uniform or gradient
tint. Although photochromic lenses may be good UV-absorbent sunglasses (again,
the label must say that), it takes time for them to adjust to different light
conditions.
"Ground
and polished"
Some non-prescription glasses are ground and polished when they are manufactured
to improve the quality of the lenses. Non-prescription lenses that are not
ground and polished will not hurt your eyes. You do want to make sure that
the lenses you buy are made properly. To judge the quality of non-prescription
sunglasses, look at something with a rectangular pattern such as floor tile.
Hold the glasses at a comfortable distance and cover one eye. Move the glasses
slowly from side to side, then up and down. If the lines stay straight, the
lenses are fine. If the lines wiggle, especially in the center of the lens,
try another pair.
"Impact
resistant"
All sunglasses must meet impact standards set by the Federal Food and Drug
Administration. No lens is truly unbreakable, but plastic lenses are less
likely than glass lenses to shatter when hit by a ball or stone. Most non-prescription
sunglass lenses are plastic. Polycarbonate plastic, used in many sports sunglasses,
is especially tough but scratches easily. If you buy polycarbonate lenses,
look for ones with scratch-resistant coatings.
Lens Darkness
A medium lens is good for day-to-day wear, but if you use the glasses for very bright conditions, choose a darker lens. The color and the degree of darkness do not tell you anything about the lenses' ability to block UV light.
Those
at Special Risk
There are some people who are at greater risk for UV-related eye damage. People
with certain eye diseases, such as macular degeneration or retinal dystrophies,
need to protect their eyes whenever they go outside, no matter how briefly.
One million Americans have cataract surgery each year. During this procedure, the eye's natural lens is removed, leaving the eye more vulnerable to UV light. During or after cataract surgery, the natural lens is usually replaced by an intraocular lens (IOL). Older intraocular lenses absorb much less UV light than ordinary glass or plastic eyeglass lenses. Manufacturers of IOLs now make many of their products UV absorbent. If you have had cataract surgery and your IOL is not the newer UV-absorbent type, you may want to wear sunglasses and a hat for added protection.
Contact
Lens Wearers
Contact lenses by themselves will not protect your eyes from UV light. Many types of contact lenses are available with UV protection. If you do not have contact lenses that absorb UV light, you still need to protect your eyes with sunglasses.
Photosensitizing
Drugs
Photosensitizing drugs — drugs that make your skin more sensitive to
light — can make your eyes more sensitive to light as well. You should
discuss precautions with your Eye Care Professional if you are taking any
of the following drugs:
Psoralens (used
in treating psoriasis);
Tetracycline;
Doxycycline;
Allopurinol;
Phenothiazine.
Wear UV-absorbent sunglasses and a hat whenever you go outside for as long
as you take the drug.
Special Situations
Ordinary sunglasses, even the best, cannot protect your eyes from certain
intense light sources. Arc welding, tanning lights, snowfields or gazing directly
at the sun (especially during a solar eclipse) can damage your eyes. Looking
at any of these light sources without adequate protection can cause a painful
corneal condition called photokeratitis or even a permanent loss of central
vision.
Cost
The best sunglasses offer 100% UV absorption, the best optical quality and
are the least likely to break. Yet they don't have to be expensive.
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