When purchasing new sunglasses, are you more concerned about looking cool or protecting your eyes from UV damage? If you said the latter, you’re among only 28 percent of Americans who are more concerned with safety than looks, according to the American Optometric Association. Exposing eyeballs to the sun can be just as unhealthy as sunbathing without sunscreen, but are sunglasses as protective as we thought?

A new study has reported that exposure to the sun may deteriorate your sunglasses over time and the lenses may become lighter and less effective against damaging rays. To reach this conclusion, researchers used an “aging test” in Europe, Brazil, New Zealand, and Australia and exposed sunglasses to a sun simulator for 50 hours from a 450-watt lamp. This exposure is equivalent to two days in a natural environment on a summer's day, or four days in winter.

Liliane Ventura, the corresponding author, from São Carlos School of Engineering, University of São Paulo, Brazil, said: "50 hours of exposure to the sun simulator equates to 23.5 hours of exposure to natural sun in Sao Paulo in Brazil. Most Brazilians replace their sunglasses every two years. To test the sunglasses are safe to wear for these two years, with the assumption they are worn for a period of two hours a day, they should be tested for 134.6 hours at a distance of 5cm. Although our calculations are mainly based on Brazilian cities, other countries may also benefit, especially those located at similar latitudes."

The research concluded that the revision of standards is needed to test sunglasses quality and establish safe limits for the lenses' UV filters.

Insufficient eye protection could damage both the cornea and the internal structure of the eye, researchers stated in the new study. UV rays can cause a swelling of the eye, called edema, or the growth of pink, fleshy tissue on the white of the eye, called pterygium. Both interfere with vision.

Too much exposure to sun can also cause cataracts, a clouding of the lense of the eye, and retina damage.

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