Are your sunglasses picked up from the roadside? Then, you could end up damaging your eyes, says DIVYA KUMAR

Anjali has three pairs of sunglasses to wear to college — one shaded in her favourite colour pink, one wraparound and one mirrored — to suit her different moods. "It's fun to be able to mix it up a little," she says. "There are so many cool styles out there."And it's not like it strains her budget. She bought them all from pavement sellers near her home, paying just Rs.120 for one and Rs. 75 for the other two. Great deal, right?Wrong. What people like Anjali who buy unbranded sunglasses cheap (the prices can go as low as Rs.10) on the roadside don't realise is that they're paying a steep price in terms of the long-term health of their eyes.Not only do these sunglasses fail to provide any protection against Ultra Violet (UV) rays, they actually increase the damage caused by the sun's rays to the cornea and the retina of the eye, according to Dr. Amar Agarwal, joint managing director, Dr. Agarwal's Eye Hospital. "Most of these sunglasses are only colour tinted, causing the eye to react as though it has entered a dark room," he explains. "The pupils dilate, so more rays enter the eye and more damage occurs."

Types of rays

Most of the damage is caused by UV-A and UV-B, two types of UV rays that are contained in sunlight. The third kind, UV-C, is completely blocked by the ozone layer, but UV-B is only partially absorbed by the ozone and UV-A isn't absorbed at all. So what happens when these rays hit your eyes? UV-B damages the cornea, the outer surface of the eye, causing cataract, while UV-A passes right through and damages the inner part of the eye, the retina. "Lack of awareness about UV is one of the reasons why people in India start developing cataracts at 50-plus whereas the average age in the U.S., for example, is 70-plus." says Dr. Agarwal. When you buy a pair of branded, tested sunglasses, you are ensuring that both UV-A and UV-B are blocked from entering your eyes. When you wear roadside sunglasses, more of the harmful rays enter your eyes through the dilated pupils. "It's better not to wear sunglasses at all rather than wear ones from the roadside," says Dr. Agarwal. "Go to a good optical shop you trust, and buy a known brand."

Consult your optician

Not all branded sunglasses provide the same level of protection against UV rays, however. They're generally divided into three kinds based on the extent of blocking of visible light and UV rays: cosmetic, general purpose and special purpose. So make sure you ask about the degree of UV protection with your optician the next time you buy sunglasses. You may also want to check out certain types of lenses that are suited for particular activities. For example, both polarised lenses and lenses with anti-reflective coating reduce reflected glare from long, flat surfaces such as the hood of a car or roads, and so are comfortable for driving. Polarised lenses are particularly useful for those who play water or snow sports for long periods. For most part, the colouring of the lenses and mirror coatings are just cosmetic; they don't really provide a particular advantage in protection. However, certain colour lenses, such as yellow or brown, can reduce distortion, which is why they're popular with sportsmen.As summer rolls around in the city and you take out the sun blocks and sunscreen to protect your skin, spare a thought for your eyes too. Sunglasses are much more than just the ultimate fashion accessories, so make an educated choice when you buy a pair this year. * * * Sun and shadeCosmetic sunglasses: Provide up to 60 percent blockage of visible light and UV-A rays and up to 95 per cent blockage of UV-B rays. They are for use in sunlight that's not too harsh.General purpose sunglasses: Block up to 92 per cent of UV-A rays and 99 per cent of UV-B rays. These provide protection in harsh sunlight and are good for use while driving.Special purpose sunglasses: Block up to 98.5 per cent of UV-A and at least 99 per cent of UV-B rays, and are used in case of prolonged sun exposure and for those at high risk for cataracts.