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UVB rays cause suntan, but can also cause skin cancer. They can encourage or accelerate eye damage and its complications. The UVA rays are dangerous as well for the eye. The thinning of the ozone layer, and the fact that people live longer, increase the risks of short term high intensity exposures as well as long term low intensity exposures. Most of the damaging effects of UVB and UVA absorbed by the eyes are cumulative. As a result, the damages increase progressively and are not reversible. Also, some people are more sensitive than others to UV rays.

The absorption of light creates heat or chemical reactions. These reactions can be damaging to the eyes when the degree of light absorbed is bigger than the eye's capacity for repair. As the UV rays contain more energy than the visible light, their absorption is more dangerous. The external eye membrane, that is the cornea and the conjunctiva, absorbs the UVB rays. The crystalline lens mostly absorbs the UVA. The retina, that is, the opaque tissues situated at the back of the eye, absorbs the visible light. If there are too many UV rays in the atmosphere, the frontal parts of the eyes can be damaged, and the visible light is too intense, the retina can suffer permanent damage, and can even suffer permanent blindness. This is what happens when looking directly at the sun for more than a few seconds.

The effect of the UV rays, together with the wind and eye dryness, can cause snow blindness (keratitis lagophtalmos and conjunctivitis), a temporary but very unpleasant disorder. Some studies show that the risk of cataract (the eye crystalline becoming gradually opaque) increases with everyday exposure to intense sunlight, more precisely to UV, for several years, mostly when light reflects on large surfaces - like the sea for example. However, some scientists do not agree on this fact. Some people are more prone to develop cataracts than others, and this might have nothing to do with UV exposure.

Blue light, that is the visible light situated in the blue spectrum, constitutes another potential danger. The eye cannot concentrate on the blue waves as well as it does for other colors. However, the brain adjusts the visual perception when the vision is slightly blurred. It has never been able to demonstrate that the blurry effect caused by the blue light could damage the eye. Studies revealed, however, that the retina can suffer photochemical damages caused by shorter wavelengths of visible light -- the blue end of the spectrum. At present, some scientists think that regular outside exposure to blue light, for several years, can age the retina and accelerate macula degeneration for sensitive people. This retina disorder is the main cause of blindness in people over 60 years of age. On the opposite, other scientists think that these fears are groundless.

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