Protecting your eyes from Ultra Violet rays
T. R. C. K. Wijayarathna (Demonstrator Department of Physics Sri
Jayawardenapura University) in this article describes how sunglasses can
be used to protect our eyes from the harmful effects of UV (Ultra
Violet) rays of the sun.
He writes: "The continuous nuclear processes inside the sun emit
electromagnetic waves and matter. These e.m. waves are at various wave
lengths. The site of a wave is measured by its wave length, which range
from very long radio waves to very strong gamma rays.
The amount of energy in an e.m. wave is proportionately related to
its wavelength. Shorter wavelengths have higher energy.
These e.m. waves if directly strike us can damage our body causing
burns, wrinkling, premature ageing and even cancer but we are fortunate
that most of these e.m. waves are absorbed by the atmosphere, so the
effects are minimised.
UV light
However, with visible light (a portion of the e.m. spectrum) some UV
(Ultra Violet) waves come to the earth's surface.
The invisible UV light is the component of sunlight most responsible
for eye damage. Too much unprotected exposure to UV waves can cause 'photokeratitis'
that like sunburn on our skin. That means photokeratitis is sunburn of
the eye.
Like sunburn on skin, eye surface burns are painful but usually
temporary. It makes the eyes red and tearful. It is also temporary. But
eye damage from the sun can happen gradually over lifetime.
Repeated exposure to bright sunlight without adequate protection can
damage the cornea which is the outer transparent part of the eye that
transmits light to the retina, the lens which is the part of the eye
responsible for focusing and retina which is the innermost layer of the
eye that transmit on image to the brain. Final result is an eye cancer.
Children spend more time outdoors than adults and their young eyes
let more UV rays inside. Fortunately, this damage can be prevented by
wearing UV eye protection.
Easy protection
Protecting ourselves and our children from the effect of UV rays is
easy. Wearing UV protected sunglasses are the best way to shield our
eyes from the sun as well as dirt, dust and other particles that can
damage the eyes. An optician can assist you in finding a pair of
sunglasses to fit your vision needs and your lifestyle.
Sunglasses and light
Sunglasses keep certain wavelengths of light from entering the eye.
They can reduce the amount of light entering the eye, protect against
harmful UV light, decrease glare and increase contrast.
And they can be helpful for people with conditions such as cataracts,
glaucoma, diabetic retinopathy, retinitis pigmentosa, albinism and
macular degeneration.
Let us see the technologies of sunglasses because it is important
when purchasing good quality sunglasses.
Polarising test
A lot of sunglasses in the market are advertised as polarising.
Whether this is true or not, you can find in a simple way. Find a
reflect surface and hold the glass, so that viewing the surface through
one of the lenses.
Now slowly rotate the glasses to a 90-degree angle, and see if the
reflective glare diminishes or increases. If the sunglasses are
polarised, we will see a significant diminishing of the glare.
Mirrored look
Sunglasses often have a mirrored look, this is the mirroring. The
lenses in these sunglasses have a reflective coating applied in a very
thin layer, which is called half silvered surface.
The half silvered surface will reflect about half the light which
strikes its surface, while letting the other half go straight through.
Common problem
A common problem with sunglasses is called back glare. This is light
that hits the back of the lenses and bounces into the eyes. Therefore an
anti-reflective coating is needed to reduce these reflections off the
lenses.
UV coating
Ultraviolet coating is most important. Intense and prolonged exposure
to UV radiation can cause either cancer of the eye or a sun burn on our
retina.
A good UV coating on our sunglasses can eliminate UV radiation, and
we should check to make sure that our sunglasses filter 100 per cent of
UV rays. There should be a statement on the label telling us how much UV
protection sunglasses have. We should choose 100 per cent protection.
Cooling glasses
Photochromic lenses which are called cooling glasses, have millions
of molecules of substances, such as silver chloride or silver halide,
embedded in them.
When exposed to UV rays and visible light, that molecules undergo a
chemical process that cause them to change colour by absorbing the UV
waves and visible light. When we go indoors and out of UV and visible
light, the reverse chemical reaction takes place and the glasses become
colourless.
Health education on new path completing two years
HEALTH EDUCATION: Taking health eduction to the public on a new path
through Medical Crosswords, which we introduced in 2004 in association
with Novartis Medical Nutrition completes two years today (November 25)
with the Draw No. 24 of the Crossword taking place at the Colombo Apollo
Hospital Auditorium at Narahenpita.
We are not boasting about it, but wish to record the fact for history
in print media's contribution of developing new avenues for health
education of the public through the media.
Here’s one HealthWatch Medical Crossword Draw No. 9 in progress at
Ceylinco Health Care Centre at Hyde Park Corner Colombo. Dr. Shama
Fernando, Head of the CD Centre picking a winner, watched by Prof.
Rohan Jayasekera (Professor of Anatomy Colombo University) chief
guest at the Draw (2nd from right), Dr. Dennis J. Aloysius (3rd
from right), Family Physician Visiting Lecturer PGIM and Member
HealthWatch Medical Advisory Panel and Madu Siriwardena (Novartis
Medical Nutrition Country Manager for Sri Lanka and Maldives.
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This fact was acknowledged at the first Medical Crossword Draw No. 1
we held at Galle Face Hotel Colombo on May 23, 2004 where the chief
guest at the event a prominent Indian Nutritionist and former Associate
Professor of Clinical Nutrition, Sri Ramachandra Medical College
commended us for having produced the first crossword puzzle in medicine
in a national newspaper in this part of the world.
"As far as I know there are a few medical crosswords carried in
medical journals for doctors, but not in a national newspaper published
for the ordinary people"
"Looking at the large number of entries sent for this first crossword
draw, is solid evidence to prove that new thinking and new approaches
are needed to carry health messages to the people where they have a role
to play" (Daily News of May 28, 2004)
World Health Day April 2005
A landmark in our medical crossword programme was, when our Draw No.
10 in April, 2005 was included as part of the official programme held to
mark the day jointly by the Health Ministry and the WHO office here at
the Mahaweli Centre in Colombo where Health Care and Nutrition Minister
Nimal Siripala de Silva and the then WHO representative in Sri Lanka,
Dr. Kan Tun were the chief guests. Both of them drew the prize winners
in this Draw and gave away prizes to winners in the previous draw no. 9.
Both of them highly commended our programme and Novartis Medical
Nutrition for sponsoring it.
We had further recognition for our medical crossword programme as a
commendable move in the health education programme, when our Draw No. 15
was held as part of the inaugural items at Sri Lanka's first National
Health Care Exhibition held at the BMICH Convention Centre, in Colombo
on May 15, 2005.
Prayer for peace
In December last year Doctors Wives' Association Sri Lanka included a
Special Draw of the Medical Crossword No. 17 to mark Christmas, where a
special prayer for peace, composed by us at the HealthWatch was recited
by a doctor's grand daughter Shinali de Mel.
We end this article with that prayer for peace in our country and
informing our readers that we are having a small programme this saturday
November 25 at the Apollo Hospital Auditorium at Narahenpita to mark the
second year anniversary of the Medical Crossword along with Draw No. 24.
The first three prize winners in the Crossword No. 12 to 23 have been
invited for this event. |