What is Ultraviolet Light?
Light energy travels through space in the form of waves,
with different types of light having different wave
lengths. Ultraviolet light rays, the damaging component
in sunlight, are so short that they aren't part of the
visible light spectrum.
How damaging is Ultraviolet Light?
In the last few years people have become much more aware
that ultraviolet light from the sun can cause injury
to the skin. Less well known is that those same ultraviolet
rays can cause eye problems. Since ultraviolet rays
are invisible, we aren't aware of them and are unable
to judge their intensity. Nonetheless, a lifetime of
exposure to sunlight can cause conjunctival, corneal,
lens, and retinal damage. Infants and young children,
with their more translucent cornea and lens, are particularly
susceptible to ultraviolet damage.
Direct sunlight is most intense in the summer months,
between 11 a.m. and 3 p.m. (daylight saving time). Ultraviolet
radiation is also greater at high altitudes and closer
to the equator. Snow, sand and open water all readily
reflect these rays, as do the glass and concrete on
buildings. This can result in increased exposure of
the eyes and face, causing damage in less time. Artificial
sources, such as welding arcs and sunlamps, have caused
damage to the eyes and skin.
What diseases can Ultraviolet Light
cause?
Over a lifetime of exposure, ultraviolet rays can cause
diseases ranging from cataracts to cancer. Although
these effects are cumulative, they can be reduced by
avoiding UV exposure.
Do sunglasses offer good protection?
Standards for sunglasses have improved dramatically
over the last few years, and today most sunglasses are
effective at screening or reflecting ultraviolet light.
Look for stickers that say the lenses provide a minimum
of 90 percent protection from UV A and 95 percent from
UV B light. Lenses tinted dark grey or dark green offer
the best results.
The most important consideration when buying sunglasses
is how well they cover the eye: large-size lenses, glasses
that fit snugly, and a wrap-around design all help reduce
damaging UV rays that can easily leak in around the
edges of inappropriate or poor-fitting sunglasses. Price
has almost no bearing on how well a pair of sunglasses
will protect you from UV light (but keep in mind that
some cheap sunglasses can have enough lens distortion
to cause eye fatigue and headaches).
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