You need sunglasses that:
Block 99 - 100% of UV-A and UV-B, which
can cause cataracts and other eye health problems.
Screen out 75 to 90% of visible light.
Are perfectly matched in colour and absorption
and free of distortion and imperfection.
Follow these sunglass buying tips:
Check lenses to be sure the tint is uniform,
not darker in one area than another. With gradient lenses,
be sure the tint lightens gradually from top to bottom.
Hold the sunglasses at arm's length. Look through them at
a straight line in the distance, such as the edge of a door.
Slowly move the lens across the line. If the straight edge
distorts, sways, curves or moves, the lens has imperfections.
It is important to recognize the sunlight is a substantial
source of UV radiation which may damage tissues of the eye.
At risk from sunlight, or strong artificial UV sources, are
the ocular surface (snow blindness and pterygium), the lens
(cataract) and the retina (eclipse blindness and macular degeneration).
Ultraviolet radiation is divided into two
major bands, UV-A and UV-B. UV-A is longer wavelength radiation,
close to blue in the visible spectrum, that usually induces
skin tanning and browning, and has been implicated in skin
aging. UV-B is more active, shorter wavelength radiation that
causes blistering sunburn and is associated with skin cancer.
Excessive exposure to intense sunlight,
or to an artificial source such as a welding arc or sun tanning
lamp, can burn the surface of the eye, (cornea and conjunctiva)
much like sunburn on the skin. The risk is highest in environments
where much UV is reflected, such as snow or water. Although
snow blindness (photokeratitis) may be painful, it is usually
self-limited with recovery in one or two days. Chronic sun
exposure also contributes to other ocular surface problems
such as pterygium.
Cataract (clouding of the lens) is a major
health problem in Europe and the most common surgical procedure
among the elderly. Globally, cataract causes half of all serious
visual impairment and affects 20 million people. Several laboratory
and epidemiological studies have suggested a link between
sun exposure and cataract. There is debate about how close
this linkage is for one common form of cataract (nuclear sclerosis)
but measures to reduce UV exposure should reduce the risk
of at least two types of cataract (cortical and posterior
sub capsular)
Macular degeneration (age related damage
in the central vision area) is the major cause of blindness
among Canadians over the age of 50, and is an increasingly
important problem as our population ages. Both UV and deep
blue light have been shown to be damaging to the retina in
laboratory studies, and a number of scientists have postulated
that UV and blue light may contribute to retinal aging and
macular degeneration. Epidemiological studies to date have
not demonstrated any clear relationship, except possibly for
some severe forms of the disease that seem associated with
a history of greater blue light exposure.
Protection from UV (including the longer
UV-A wavelengths) and from too much blue light may thus be
prudent.
Just wearing a hat will reduce exposure
by roughly half. Sunglasses are capable of eliminating virtually
all of the UV.
Recommendations:
The public should protect their eyes, especially
when exposed to excessive sunlight. If there is sufficient
UV present to cause sunburn, sunglasses are advised.
People with high UV exposure, especially
those spending prolonged time in the sun or in the snow during
the middle of the day, or those exposed to intensive artificial
sources such as welding arcs or sun tanning lamps, should
consider using close-fitting goggles or sunglasses with lenses
that absorb all UV-B and UV-A radiation, and a substantial
portion of the blue light as well.
Consumers should be able to determine the
UV and visible light absorptive properties of sunglasses.
Manufacturers are encouraged to adopt a simple coding system
for the sunglasses that clearly indicates the degree of UV-B
and UV-A radiation, as well as the blue and visible light
absorption.
Brites Sunglasses conform to the
British Standard BS EN1836(1997). |
