diffraction glasses .pdf
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Sun glasses 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).
From 10 a.m. until 2 p.m. the sun is high and Ultraviolet light is the strongest The closer
you are to the earth’s equator; the higher altitude, and the more reflective the surface,
the stronger it is. Ultraviolet rays pass through clouds, so don’t be fooled into thinking
protective eyewear isn’t necessary when the sky is cloudy. UV rays also reflect from
walls, roads, snow and sand and your eyes can suffer from high energy light waves
even in shaded areas
The sun has damaging ultraviolet rays that can cause photokeratitis, pingueculae and
permanent retinal damage, so your glasses should protect your eyes from ultraviolet.
Shades which do not filter out UV light can actually cause more damage to the eye than
no sunglasses at all. Eyes behind shades dilate and more UV light reach the retina,
unprotected exposure to ultraviolet light can lead to serious eye problems. It is
important to protect your eyes and you should always look for the marking when buying
a pair of sunglasses. Most shades will have a sticker or a tag as well showing that they
filter out 99% or 100% of ultraviolet.
Polarized shades are coated with a special film that helps reduce glare. Having this
chemical film on polarized a pair of sunglasses, you are able to see more clearly.
Polarized sunglasses have been popular for years with boaters and fishermen who need
to reduce reflected glare from the water surrounding them (see also diffraction glasses).
When choosing sunglasses, better to invest in wraparound frames, they limit sunlight
more effectively; protection of UVA and UVB rays should be 99 to 100%; gray or
brown are the best for color recognition. The darkness of your lenses has no effect on
UV protection. People with eye disorders such as cataracts, macular degeneration and
retinal disease are especially susceptible to UV rays and should take extra precaution.