May 10 2018
Shades are one of protective eyewear type that is designed to prevent high-energy UV light and bright sunlight from discomforting and damaging the retina and eyes. (The New Partridge Dictionary of Slang and Unconventional English. Partridge, Eric, Tom Dalzell, Terry Victor). In the early 20th century, they were also known as sun cheaters (American slang).
The American Optometric Association suggests when purchasing sunglasses, consider the following: 99 to 100% protection of UVA and UVB rays; screen out 75 to 90 percent of visible light; gray or brown for proper color recognition. The darkness of your lenses has no effect on UV protection. A pair of sunglasses are especially necessary for people with macular degeneration, cataracts, etc.
One of important features of your a pair of sunglasses is protecting your eyes from UV light from the sun. If ultraviolet light passes through the sunglasses, it causes more damage then eyes without shades at all. Eyes behind shades dilate and more ultraviolet light reach the retina, unprotected exposure to UV light can lead to serious eye problems. It is important to protect your eyes and you should always look for the marking when buying sun lenses. Now many shades block 99-100% of ultraviolet light
From 10 a.m. until 2 p.m. the sun is high and UV light is the strongest UV rays are also stronger at high altitudes and against the reflective surfaces of snow and water. Even if the sky is cloudy, UV may be dangerous for your eyes and you should use protective shades. Even though shaded areas reduce Ultraviolet exposure, your eyes can still be exposed to rays that bounce from buildings, roads and other surfaces.
The United States Environmental Protection Agency (EPA) developed the ultraviolet Index, and to protect your eyes from harmful solar radiation, shades should block up to 100 percent of UV rays. High ultraviolet protection glasses don't have to be expensive. Generally, more expensive lenses have higher quality and provide a sharper, clearer image with less distortion. UV light is in wavelengths UVA (up to 400 nm) and UVB radiation (290 to 320 nm), both can be harmful to your eyes.
Polarized a pair of sunglasses are coated with a special film that helps reduce glare. Polarization reduces glare coming off reflective surfaces like water or pavement, this does not offer more protection from the sun, but can make activities like driving or being on the water safer or more enjoyable. Besides boaters, skiers, bikers, golfers and joggers benefit the most from polarized sunglasses.