UV rays are one of the known causes of cataracts, a gradual clouding of the eye lens that destroys vision. The effects of sunlight on the eye are cumulative and depend on the length of time spent in the sun. For example, farmers are more likely to develop cataracts sooner than office workers.

Experts say that sunglasses help prevent cataracts. They recommend wearing them whenever the light is bright enough to make you squint, even on cloudy days and especially at high elevations.

Most sunglasses list absorption figures or UV protection figures on their labels. Good colours for sunglasses are gray, green or brown. Gray lenses do not distort primary colours so they are good for driving. Green lenses let the maximum amount of useful light reach the eyes on an overcast day, and brown lenses sharpen detail and provide better protection against glare.

Wrap-around frames protect your eyes from all angles and are a good choice if you are in the sun all day. Polarised lenses cut reflected glare, and are perfect for skiing, boating and the beach.

For children’s sunglasses, look for shatterproof lenses in addition to the above features ¡ª they are also a good idea for adults who are rough on sunglasses or who play sport.

The sun’s damage to the eyes does not stop with cataracts. Exposure to both visible light and UV radiation is also a factor in the gradual degeneration of the retina and in sunburn of the cornea.