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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.

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.

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