Hyderabad Blues: [HM:252819] Sun Glasses - Frequently Asked Questions

If the sun doesn't bother my eyes, do I still need to wear sunglasses?

Yes. The sun has damaging UV rays that can cause photokeratitis, pingueculae and permanent retinal damage.

What exactly are UV rays?

Ultraviolet (UV) rays are located just past the violet portion of the visible light spectrum; sunlight is the main source. UV light is broken into three different types: UVA, UVB and UVC.

UVA has longer wavelengths and passes through glass easily; experts disagree about whether or not UVA damages the eyes.
UVB rays are the most dangerous, making sunglasses and sunscreen a must; they don't go through glass.
UVC rays do not reach the Earth because its atmosphere blocks them.

When do UV rays affect my eyes?

Most people think that they're at risk only when they're outside on a sunny day, but UV light can go right through clouds, so it doesn't matter if the sky is overcast. The sun's rays are strongest between 10 am and 2 pm.

Glare and reflections can give you trouble, so have your sunglasses ready if you'll be around snow, water or sand, or if you'll be driving (windshields are a big glare source).

The following put you at additional risk: sunlamps, tanning beds and parlors, photosensitizing drugs and living at high altitudes or near the equator. To find out how high the UV light levels are today where you live, here's a UV index map for the United States, updated twice a day by AccuWeather.

Can certain medical problems increase my risk for damage from UV rays?

Yes. People with cataracts (or who have had cataract surgery), macular degeneration and retinal dystrophies should be extra careful. Read more about these conditions in our Eye Problems and Diseases section.

What are my options to prevent UV damage to my eyes?

You must wear sunglasses to prevent damage to your eyes. While some contact lenses provide UV protection, they don't cover your whole eye, so you still need sunglasses.

Look for sunglasses that protect you from 99 to 100 percent of both UVA and UVB light. This includes those labeled as "UV 400," which blocks all light rays with wavelengths up to 400 nanometers. (This covers all of UVA and UVB rays.)

Also, you may want to consider wraparound sunglasses to prevent harmful UV rays from entering around the frame.

What are the different kinds of lenses that are available?

With so many lenses available, it's a good idea to ask a professional optician for help when choosing sunglasses. Different tints can help you see better in certain conditions, and a knowledgeable optician can help you choose sunglass tints that are best suited for your needs.

Blue-blockers block blue light and usually have amber lenses. Some evidence indicates blue light is harmful, and could increase risk of eye damage from diseases such as macular degeneration. These lenses are popular among skiers, hunters, boaters and pilots who use them to heighten contrast.

Both polarized lenses and anti-reflective coating cut reflected glare. Polarized lenses in particular are popular with those who play water and snow sports. Anti-reflecting coatings reduce glare caused by light reflecting off the back surface of your sunglass lenses.

Mirror-coated lenses limit the amount of light entering your eyes, so you're more comfortable.

Mirror coatings (also called flash coatings) are highly reflective coatings applied to the front surface of sunglass lenses to reduce the amount of light entering the eye. This makes them especially beneficial for activities in very bright conditions, such as snow skiing on a sunny day.

The mirrored sunglasses associated with state troopers are one example of a flash coating. The technology has advanced, however, so that today's choices in mirror coatings include all colors of the rainbow, as well as silver, gold and copper metallic colors. Hot pink, blue — almost any color is available.

Choosing the color of a mirror coating is a purely cosmetic decision. The color of the mirror coating you choose does not influence your color perception — it's the color of the tinted lens under the coating that determines how mirrored sunglasses affect your color vision.

What about sunglasses blocking infrared rays?

Infrared rays are located just past the red portion of the visible light spectrum. Though infrared radiation produces heat, most experts agree that the sun's infrared rays do not pose a danger to the eyes.

Which lens color is the best?

Lens color is a personal choice and doesn't affect how well sunglass lenses protect your eyes from UV light. Gray and brown are popular because they distort color perception the least.

Athletes often prefer other tints for their contrast-enhancing properties. For example, yellow lenses are popular with skiers and target shooters because they work well in low light, reduce haze and increase contrast for a sharper image.

Children don't need sunglasses, do they?

Children's sunglasses are essential. Children are at particular risk because they're in the sun much more than adults, and their eyes are more sensitive as well. UV damage is cumulative over a person's lifetime, which means you should begin protecting your child's eyes as soon as possible.

Most parents would not allow their children to go outside without shoes, yet many seem unaware of the need to protect their children's eyes.

I wear glasses. What options are available to me?

You can buy prescription sunglasses or glasses with photochromic lenses (which change from clear to dark) from your eye care practitioner. Clip-ons may be a less expensive option, and can be bought at the same time as your regular eyeglasses to perfectly match the frames.

Some eyeglass frames include sun lenses that magnetically attach to the frame. This gives you the convenience of clip-on sunglasses with less risk of scratching your prescription lenses.

http://www.allaboutvision.com/faq/sunglasses.htm#ixzz1MrmJYso1

M Junaid Tahir

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