Sunglasses


spot_o9Is it Important To Wear Sunglasses?

Ultraviolet Radiation Despite the fact that the sun is over 93 million miles away, its rays also pose important health and ocular dangers. The principal danger posed by the sun is in the form of
ultraviolet radiation, or for short, UV radiation. UV radiation is a component of solar
energy, but it can also be given off by artificial sources like welding machines, tanning
beds and lasers. You are probably aware of the danger posed by UV radiation to your
skin, but you may not realize that. exposure to UV radiation can harm your eyes and
affect your vision as well. UV radiation is divided into several classes: UV-A, UV-B and
UV-C.

UV-C radiation originating from the solar system is absorbed by the ozone layer in the
earth’s atmosphere and does not present any threat. This is in contrast to man made
sources of UV-C, such as electric welding arcs, which are very harmful to the eyes if you
do not use proper protection. This absorption though is not true of UV-A and UV-B. More
and more scientific evidence is showing that exposure to both UV-A and UV-B can have
damaging long and short term effects on your eyes and vision.

 

If you are exposed, unprotected, to excessive amounts of UV radiation over a short period
of time, i.e. a tanning booth without protective eyewear, you are likely to experience an
effect called photokeratitis. Like a “sunburn of the eye” it may be painful and you may
have symptoms including red eyes, a foreign body sensation or gritty feeling in the eyes,
extreme sensitivity to light and excessive tearing. Fortunately, this is usually temporary
and rarely causes permanent damage to the eyes.

 

Long term exposure to UV radiation can be much more serious. A number of scientific
studies and research have shown that exposure to small amounts of UV-B radiation over a
period of many years contributes to the development of cataract s; pterigia (tissue growth
on the surface of the eye); skin cancer around the eye; and can cause damage to the retina
(macular degeneration), the nerve-rich lining of your eye that is used for seeing. Damage
to the retina is usually not reversible.

 

While everyone is at risk of the harmful effects of UV-A and UV-B radiation, certain
people are at an increased risk because the effects of UV radiation are cumulative. This
means the longer your eyes are exposed to UV radiation, the greater the risk of
developing conditions such as cataracts in later life. Therefore, you should wear quality
sunglasses that offer good protection and a hat or cap with a wide brim whenever you are
working outdoors, participating in outdoor sports, taking a walk, running errands or doing
anything in the sun.
Sunglasses

Sunglasses have been popular with people for years, both for comfort and as a fashion
accessory. However as studies and research continue to demonstrate a relationship
between UV-A/UV-B exposure and ocular disease, the protection of the long-term health
of your eyes is yet another reason to wear sunglasses. In order for sunglasses to provide
adequate protection for your eyes, they should:

 

  • Block out 99 to 100 percent of both UV-A and UV-B radiation;
  • Screen out 75 to 90 percent of visible light;
  • Have lenses perfectly matched in color and free of distortion and imperfection;
  • Have lenses that are gray, green or brown.

 

 

 

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. These lenses are very soothing for eyes that are sensitive
to glare, and are highly recommended.

 

“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 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 lenses are a must for your sunglasses if you participate in
potentially eye hazardous work or sports. These lenses provide the most impact
resistance. Polycarbonate plastic, though tough and used in many sports sunglasses,
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.

 

Cataract Surgery Patients

 

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 –may also make
your eyes more sensitive to light as well. You should discuss precautions with your
ophthalmologist if you are taking any such drug. You should also 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. Discuss you vision requirements and
lifestyle to the optician who is able to design the best possible combination of frames and
lenses for your particular needs.

 

Be sure to see your eye doctor routinely for a thorough eye examination. It is a good way
to monitor our eye health, maintain good vision and keep track of your UV radiation
protection needs as well as new advances in that protection.