ultraviolet rays (UV) have shorter wavelengths and more energy than visible light rays. They can have a harmful effect on the eyes immediately or cumulatively from regular exposure over a number of years. UV has been divided into three bands according to wavelength: UVA, UVB, UVC.
the body reacts less strongly to UVA, however much more UVA than UVB reaches the atmosphere. UVA is transmitted by the cornea, which repairs itself quickly, but absorbed by the eye crystalline lens whose cells do not repair as quickly, so UVA damage builds over time. 1% of UVA reaches the retina, which does not repair itself.
is the most immediate and painful form of UV. It consists of very high-energy wavelengths, not entirely absorbed by the atmosphere. The cornea absorbs UVB which causes many eye diseases.
is the shortest, most energetic and probably most harmful of the UV rays. UVC is blocked by the upper atmosphere (the ozone acts as a UV filter) and never reaches the earth. If sunglasses protect against UVB they also protect against any possible exposure to UVC.