Though the ozone absorbs most of the ultraviolet radiations falling on it, 99% of the UVA enters the earth's atmosphere. With the gradual depletion of the ozone layer, UVB rays are also speedily coming into our atmosphere.
UV rays and eyes
The eye damaging UV Rays
Ultraviolet rays are not just problematic to human skin but can also be extremely fatal to our eyes. The UVB rays combined with cold wind and snow can cause snow blindness or photokeratitis. It is a temporary blindness that is quite painful and occurs due to some problem in the cornea. UVB rays can also lead to eye growths such as pingueculae and pterygia. Pingueculae is a yellowish patch or swelling on white of eye near cornea while Pterygium is a fleshy growth of conjunctiva on the cornea that can slowly cause complete blindness. It is by and large believed that regular exposure to UVB rays for long hours and for several years can cause cataracts (slow clouding of the lens of the eye) in eyes of that person.
Most of the UVA rays are absorbed within the lens of human eye. But the dangerous effect of these rays is a topic of much debate over which there is no unanimity as yet.
UV Rays and eye protection
The American Academy of Ophthalmology which is the world's largest association of the eye physicians and surgeons so far, recommends people to protect their eyes from the destructive UV rays with the use of sunglasses that have lenses to absorb or block 100% the UVA and UVB rays falling on them. Sunglasses are a simple and effective means to ensure safety and so long life for your eyes.
But prior to purchasing a pair of sunglasses several things should be considered. Firstly, go for the sunglasses that provide at least 98% protection from both the UVA and the UVB rays. Secondly the sunglasses should fit you closely to prevent the entry of UV rays from above. You can also go for larger lenses or wrap around sunglasses that block sunlight entering from the sides. Finally remember that there is no relation between dark color of the lenses and better UV protection. Similarly the high priced sunglasses might not offer desired protection from the UV rays.