Sunglasses
are no longer a fashion fad. They are essential in preventing
eye damage caused by the suns ultra violet radiation. While most
of us are aware of sunburn, that leads to skin cancer, medical
evidence shows that our eyes also can suffer from 'sunburn which
can lead to cataracts - a leading cause of blindness.
Children and
young adults are especially at risk and parents should make sure
their children wear sunglasses - particularly when levels of UV
radiation are high, such as on the beach, in water and in snow,
where there is additional danger due to reflection.
What
is UV radiation?
UV radiation
is a component of solar energy, as is visible light and infra
red radiation (heat). Other sources of UV radiation include welding
arcs, high intensity mercury vapour lights and even tanning lamps.
UV radiation
consists of three main types: UVA, UVB which causes sunburn and
is largely responsible for causing skin cancer. Most solar UV
radiation striking the Earth is absorbed by the ozone layer but
it has been calculated that a one per cent decrease in the amount
of atmospheric ozone will increase UVB levels by about two per
cent.
According
to predictions of the Australia National Health and Medical Research
Council, more than 36,000 additional cases of eye problems a year
will occur as a result of ozone depletion. A one per cent rise
in UV radiation levels would increase the annual incidence of
pterygia eye disease in Australia by 26,000 cases.
Effects
of UV radiation on the cornea
Most UV radiation
striking the eye is absorbed by the cornea and high UV levels
such as those encountered in the snow or on the beach can cause
it to become inflamed.
The condition
is extremely painful and causes the eye to be highly sensitive
to any light source. Although extremely uncomfortable, the condition
usually resolves itself in about 48 hours and it is advisable
to have an eye examination by an optometrist or ophthalmologist
(eye surgeon) to ensure that no other damage has occurred.
Effects
of UV radiation on the conjunctiva.
Short term
exposure to UV radiation can damage the conjunctiva, while long-term
exposure can cause it to thicken, forming a fleshy growth known
as a pterygium. Progress of this condition is usually slow, growing
until it starts to cover part of the cornea when it can interfere
with vision as well as becoming unsightly.
The only treatment
is surgical removal, which is a relatively minor procedure. The
eye should be examined by an expert in order to differentiate
between pterygia and other, more serious growths.
Effects
of UV radiation on the lens
UV radiation,
particularly the UVB type, has been shown to be associated with
the formation of cataracts. These are opacities which form in
the lens of the eye and interfere with vision, as though you were
looking through a dirty window.
In severe
cases, cataracts can be removed surgically and the old, clouded
lens replaced by an artificial one. Cataracts have always been
more common among elderly people and were thought to be a natural
result of ageing. However, recent research suggests that while
this may be partly true, they are much more likely to be caused
by prolonged exposure to UV radiation, which also can damage the
eye retina - the delicate nerve-rich lining of the eye used for
seeing. Most forms of retinal damage are irreversible.
How
to avoid the effects of UV radiation
The simplest
way of protecting your eyes from UV radiation is by limiting your
exposure to it.
The three
best ways of doing this are:
Which
sunglasses should you choose?
All the sunglasses
on sale in Australia must meet an Australian Standard which specifies
how much UV they must block.
Sunglasses
should have a tag stating they meet ANSI Z80.3-1996. The general
purpose category is for sunglasses designed for use in normal
situations where exposure to the sun is not prolonged. Specific
purpose units are intended for people exposed to high levels of
UV radiation and provide maximum protection in various sports
such as skiing or in special occupations such as flying.
Your optometrist
has access to manufacturers' technical information and depending
on your needs and lifestyle, will be able to advise you which
sunglasses suit you best. Sunglasses should be close-fitting to
prevent radiation getting around the edges of frames. Wrap-around
models are excellent.
Should
children wear sunglasses?
Children are
particularly at risk from UV radiation because they spend so much
of their time outdoors and are not aware of the danger it poses.
It is up to parents to protect their children's eyes by ensuring
they wear a hat and a good quality pair of sunglasses.
Be careful
when choosing sunglasses for children. Sometimes what appears
to be sunglasses will be 'toy' models which provide no protection
at all. Always check the sunglasses comply with the Australian
Standard
