Ultraviolet (UV) rays carry more energy than do visible light rays. Thus the eye has a greater risk of damage from absorbing UV radiation than from absorbing other forms of visible light. Two types of UV rays reach the earth s surface: UV-A and UV-B. UV-A rays are the rays emitted from the sun that contribute to premature aging and they are present year-round. They contribute to early wrinkling of the skin the development of cataracts and the progression of age-related macular degeneration. UV-B rays are the rays that cause skin cancers cataracts and photokeratitis or sunburn of the eye. These rays are stronger during the summer months. Most of the damage caused to eyes by UV-A and UV-B rays occurs gradually and is irreversible. Sensitivity to UV rays varies from person to person. Certain prescription and over-the-counter drugs might increase sensitivity. Eyecare professionals physicians and pharmacists can offer advice on the medications that contribute to sensitivity.
Sunglasses that block UV rays will reduce the likelihood of eye damage as they filter out both types of harmful rays. For the best level of protection select sunglasses that block UV-A and UV-B rays between 290 and 400 nanometers (nm) or that block at least 98 per cent of both types of UV rays. It is important to note however that labelling standards for sunglasses are voluntary and not mandatory. The darkness shade or tint of sunglasses does not indicate their ability to block UV rays. Only an invisible UV protective coat applied during the manufacturing stage or built into the lens can accomplish this.
Ironically sunglasses that have not been treated for UV rays may be more detrimental to your eyes than not wearing sunglasses at all. Dark lenses reduce the amount of light entering the eye causing the pupil to dilate. This exposes the inside of your eye to more UV radiation than without the sunglasses. It is extremely important to ensure that your sunglasses have appropriate UV protection especially for children and adults who spend a lot of time outdoors. Quality sunglass manufacturers can apply this protective coat to lenses of different materials designs and tints.