Snow, sand and open water all readily reflect these rays, as do the glass and concrete on buildings. This can result in increased exposure of the eyes and face, causing damage in less time. Artificial sources, such as welding arcs and sunlamps, have caused damage to the eyes and skin. Over a lifetime of exposure, ultraviolet rays can cause diseases ranging from cataracts to cancer. Although these effects are cumulative, they can be reduced by avoiding UV exposure.
Prescription eyeglasses vary widely in their ability to screen out harmful ultraviolet light.
Tests indicate that plastic lenses generally offer considerably better protection than their glass counterparts. Some tests indicate that soft contact lenses are the weakest protectors of all, transmitting more than half of the existing ultraviolet light directly into the eye. You should always use UV protective eyewear if you are likely to be exposed during activities such as skiing, sailing or hiking. Do not assume your regular prescription eyewear will provide adequate protection. Standards for sunglasses have improved dramatically over the last few years, and today most sunglasses are effective at screening or reflecting ultraviolet light.