ULTRA VIOLET RAYS & EYES

Ultraviolet (UV) rays are part of electro-magnetic radiation. They are invisible rays lying beyond the violet end of the visible spectrum.
Scientific research has linked several eye diseases to damage from UV light. These diseases include cataract, macular degeneration,pterygium and cancer, to name a few disorders.
The eyes are particularly sensitive to UV radiation. Even a short exposure of a few seconds can result in a painful, but temporary condition known as photokeratitis and conjunctivitis.
Photokeratitis is a painful condition caused by the inflammation of the cornea of the eye.Eyes water and vision may be blurred.
Conjunctivitis is the inflammation of the conjunctiva which becomes swollen and produces a watery discharge. It causes discomfort rather than pain and does not usually affect vision.

Ways to limit exposure the sun's UV radiation include avoiding working in the sun wearing protective clothing and hats, and applying sunscreens.

Protective clothing can include long pants, hats, and long-sleeved shirts. Some newer, sun-resistant fabrics are more efficient in blocking UV radiation.

Sunscreens are rated according to Sun Protection Factor (SPF), an index of protection against reddening of the skin).

* SPF 15 sunscreen may absorb more than 92 percent of UVB radiation.
* SPF 30 sunscreen may absorb 96.7 percent.

* SPF 40 sunscreen may absorb 97.5 percent of UVB radiation

To protect your eyes from harmful solar radiation, sunglasses should block 100 percent of UV rays and also absorb most HEV rays. Frames with a close-fitting wraparound style provide the best protection because they limit how much stray sunlight reaches your eyes from above and beyond the periphery of your sunglass lenses.
The amount of UV protection sunglasses provide is unrelated to the color and darkness of the lenses. A light amber-coloured lens can provide the same UV protection as a dark gray lens. Your eye specialist can verify that the lenses you choose provide 100 percent UV protection.

But for High-Energy visible(HEV) radiation protection, colour does matter. Most sunglass lenses that block a significant amount of blue light will be bronze, copper or reddish-brown (see lens tint guide).

Again, your eye specialist can help you choose the best "blue-blocking" lenses.


More information:http://www.allaboutvision.com/sunglasses/spf.htm