Protecting the skin outdoors from the harmful effects of Ultraviolet (UV) radiation are known to decrease the risk of skin cancer, similarly it is vitally important to protect the eyes from the harmful effect of UV. 80% of the information we process through our lifetime is received through our eyes, the most important of our senses. The sun's primary danger is in the form of ultraviolet (UV) radiation. Artificial sources, like welding machines, tanning beds and lasers, can also produce UV radiation. Extended exposure to the sun's UV rays has been linked to eye damage, including cataracts, pingueculae, pterygia and photokeratitis that can cause temporary vision loss. New research suggests the sun's high-energy visible (HEV) radiation (also called "blue light")may increase your long-term risk of macular degeneration.

Solar radiation that reaches the surface of the eye is focused and concentrated by the cornea, the clear outermost layer of the eye. Studies show that this UV radiation, which can reach the eyes from above, below and the sides, may cause changes to the tissue on the opposite side of the eye. Small tissue elevations, called pingueculea and pterygia are common in areas where there is a high degree of UV radiation. This UV radiation can also damage the sensitive skin of your eyelids. Certain medications, such as tetracycline, sulfa drugs, birth control pills, diuretics and tranquilizers, can increase your body's sensitivity to UV and HEV radiation. Surprisingly, cloud cover doesn't affect UV levels significantly. Your risk of UV exposure can be quite high even on hazy or overcast days.

Although UV protective coating layers can be applied to clear spectacle lenses, to best protect your eyes from the sun's harmful UV and HEV rays, always wear good quality sunglasses when you are outdoors. Look for sunglasses that block100 percent of UV rays and that also absorb most HEV rays. Your eyecare practitioner can help you choose the best sunglass lenses for your needs.

The damage to our eyes and skin from solar UV radiation is cumulative, meaning the danger continues to grow as we spend time in the sun throughout our lifetime. With this in mind, it's especially important for kids to protect their eyes from the sun. Children generally spend much more time outdoors than adults. In fact, some experts say that because children tend to spend significantly more time outdoors than most adults, up to half of a person's lifetime exposure to UV radiation can occur by age 18. (Other research cited by The Skin Cancer Foundation says slightly less than 25 percent of our lifetime exposure to UV radiation is sustained during childhood.) Children are also more susceptible to retinal damage from UV rays because the lens inside a child's eye is clearer than an adult lens, enabling more UV to penetrate deep into the eye. For this reason, make sure your kids' eyes are protected from the sun with good quality sunglasses. Also, encourage your child to wear a hat on sunny days to further reduce UV exposure.

Some contact lenses offer additional protection. These contact lenses absorb UV radiation by reducing the amount of radiation that reaches the surface of eye. The contact lenses also protect the eye from the radiation that comes from above or around the sides of sunglasses. Even though your contact lenses block UV rays, you still need sunglasses. UV-blocking contacts shield only the part of your eye under the lens. UV rays still can damage your conjunctiva, (the white parts of your eye), and other tissues not covered by the lens. Wearing sunglasses protects these delicate tissues and the skin around your eyes from UV damage.

UV Radiation Levels

If you can answer "yes" to one or more of the following questions, you could be at higher risk for harm to the eyes from UV radiation:

1. Do you spend a great deal of time outdoors?
2. Do you spend time skiing, mountain climbing or at the beach?
3. Do you use a sunlamp or tanning parlor?
4. Do you live in the mountains or the U.S. Sunbelt?
5. Are you a welder, medical technologist or do you work in the graphic arts or in the manufacture of electronic circuit boards?
6. Have you had cataract surgery in one or both eyes?
7. Do you take prescription or over-the-counter drugs that can increase your sensitivity to UV radiation? (If you are unsure, check with your optometrist, pharmacist or physician.).

The three categories of invisible high-energy UV rays are:

1. UVC rays. These are the highest-energy UV rays and potentially could be the most harmful to your eyes and skin. Fortunately, the atmosphere's ozone layer blocks virtually all UVC rays. But this also means depletion of the ozone layer potentially could allow high-energy UVC rays to reach the earth's surface and cause serious UV-related health problems. UVC rays have wavelengths of 100-280 nanometer(nm).
2. UVB rays. These have slightly longer wavelengths (280-315 nm) and lower energy than UVC rays. These rays are filtered partially by the ozone layer, but some still reach the earth's surface. In low doses, UVB radiation stimulates the production of melanin (a skin pigment), causing the skin to darken, creating a suntan, but in higher doses, UVB rays cause sunburn that increases the risk of skin cancer. UVB rays also cause skin discolorations, wrinkles and other signs of premature aging of the skin.
3. UVA rays. These are closer to visible light rays and have lower energy than UVB and UVC rays. But UVA rays can pass through the cornea and reach the lens and retina inside the eye. Developed by the NWS and EPA, the UV Index predicts each day's ultraviolet radiation levels on a simple 1 to 11+ scale.

This UV Index devised by the Environmental Protection Agency and National Weather Service provides a color-coded warning system to alert people to the dangers of being outdoors on certain days.

Depending on your outdoor lifestyle, you also may want to explore performance sunglasses or sport sunglasses. The amount of UV protection sunglasses provide is unrelated to the color and darkness of the lenses. For example, a light amber-coloured lens can provide the same UV protection as a dark gray lens. Your optician can verify that the lenses you choose provide 100 percent UV protection.

Sunglasses are important especially in winter, because fresh snow can reflect 80 percent of UV rays, nearly doubling your overall exposure to solar UV radiation. If you ski or snowboard, choosing the right ski goggles is essential for adequate UV protection.

When buying sunglasses, the only assurance we have of their UV protection is what’s on the label and this can be as vague as ‘absorbs UV’. Even if your new sunglasses have a reliable safety rating, UV protection can wear off. Just as you need to re-apply sun cream, your sunglasses UV protection can also fade with time. So, how do you know when it’s time to retire your much loved shades?

To provide adequate protection here are some top tips for picking your sunglasses:

1. Look for sunglasses that block 99% or 100% of all UV light. UV absorption up to 400nm is equal to 100% UV absorption.
2. screen out 75 to 90 percent of visible light.
3. have lenses that are perfectly matched in color and free of distortion and imperfection.
4. Larger frames, wraparound and closer fitting styles provide better protection from stray light.
5. A higher price tag doesn’t guarantee quality. Cheaper sunglasses can offer superior eye protection over expensive counterparts.
6. Polarized lenses help cut glare, but do not add sun protection.
7. If you participate in potentially eye-hazardous outdoor work or sports, your sunglass lenses should be made from polycarbonate or Trivex® material.
8. If your sunglasses are old, ask your optician to test their UV protection.