What is Ultraviolet Light?
Light energy travels through space in the form of waves, with different types of light having different wave lengths. Ultraviolet light rays, the damaging component in sunlight, are so short that they aren't part of the visible light spectrum.
How damaging is Ultraviolet Light?
In the last few years people have become much more aware that ultraviolet light from the sun can cause injury to the skin. Less well known is that those same ultraviolet rays can cause eye problems. Since ultraviolet rays are invisible, we aren't aware of them and are unable to judge their intensity. Nonetheless, a lifetime of exposure to sunlight can cause conjunctival, corneal, lens, and retinal damage. Infants and young children, with their more translucent cornea and lens, are particularly susceptible to ultraviolet damage.
Direct sunlight is most intense in the summer months, between 11 a.m. and 3 p.m. (daylight saving time). Ultraviolet radiation is also greater at high altitudes and closer to the equator. 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.
What diseases can Ultraviolet Light cause?
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.
Do sunglasses offer good protection?
Standards for sunglasses have improved dramatically over the last few years, and today most sunglasses are effective at screening or reflecting ultraviolet light. Look for stickers that say the lenses provide a minimum of 90 percent protection from UV A and 95 percent from UV B light. Lenses tinted dark grey or dark green offer the best results.
The most important consideration when buying sunglasses is how well they cover the eye: large-size lenses, glasses that fit snugly, and a wrap-around design all help reduce damaging UV rays that can easily leak in around the edges of inappropriate or poor-fitting sunglasses. Price has almost no bearing on how well a pair of sunglasses will protect you from UV light (but keep in mind that some cheap sunglasses can have enough lens distortion to cause eye fatigue and headaches).