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Sunglasses:
What You Need To Know.
A number of
scientific studies indicate
that spending long hours in
the sun without eye
protection can damage your
eyes by contributing to
cataracts, macular
degeneration, and growths on
the eye, including cancer.
Based on these studies,
ophthalmologists recommend
that you wear 99% and above
UV-absorbent sunglasses and
a brimmed hat whenever
you're in the sun for long
periods of time.
When to wear
sunglasses.
Sunglasses
should be worn anytime you
are outdoors, particularly
under these
circumstances: during the summer, when
the level of ultraviolet
radiation (UVA and UVB) is
at least three times higher
than
winter;
when at the beach or in the
water; when participating in
winter sports, especially at
high altitudes;
when using medications
that can cause photosentivity.
What to look
for when purchasing
sunglasses.
Most
sunglasses are designed to
protect our eyes from the
sun's harmful effects.
Ooften the labels on
sunglasses promise
protection from ultraviolet
light and other kinds of
natural radiation. It is
important to know what kind
of light you need to protect
your eyes from and what type
of light is not necessarily
harmful.
*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. UVB
radiation is considered more
dangerous to the eyes and
skin than UVA radiation.
Both plastic
and glass lenses absorb some
UV light, but absorption can
be improved by adding
chemicals to the lens
material during
manufacturing or by applying
special lens coatings. Look
for sunglasses that block
99% or 100% of all UV light.
Ssome manufacturers' labels
say "absorption up to
400nm." This is the same
thing as 100% absorption.
*GROUND AND
POLISHED:
Some
nonprescription glasses are
ground and polished to
improve the quality of the
lenses. Nnonprescription
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
nonprescription 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
(FDA) for safety. No lens is truly
unbreakable, but plastic
lenses are less likely than
glass lenses to shatter when
hit by a ball or stone. Most nonprescription
sunglass lenses are plastic.
Polycarbonate plastic, used
in many sports sunglasses,
is especially tough, but it
scratches easily. If you buy
polycarbonate lenses, look
for ones with
scratch-resistant coatings.
*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
protection.
*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 light.
*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.
Photochromic lenses come in
a uniform or gradient tint.
Although photochromic lenses
may be good UV-absorbent
sunglasses (again, the label
must state this benefit), it
takes time for them to
adjust to different light
conditions.
*WRAPAROUND
STYLE:
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
LENSES:
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. They're not as
good, however, at reducing
glare in snowy surroundings
or at the beach. 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.
*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. blocks
90% of infrared rays.
Infrared wavelengths are
invisible and produce heat.
Sunlight has low levels of
infrared rays, and the eye
tolerates infrared well.
Some sunglass 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.
Content
Provided By The American
Academy Of Opthalmology
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