Study: Replace sunglasses every 2 years

Everyone has that favorite pair of sunglasses but if you've been hanging onto those shades for a while, researchers now say it is probably time to let them go if you want to keep your eyes healthy.

A new study out of Brazil suggests you should swap out your sunglasses -- no matter the size, the shape, discount or designer -- after two years. Any longer, and you've had them for too long.

Scientists at the University of São Paulo developed what they call an aging test using a sun simulator lamp to find out how well sunglasses hold up against UV rays. It found that lenses start to wear down in about two years, exposing your eyes to dangerous UV rays.

Dr. Mark Fromer, an ophthalmologist with Lenox Hill Hospital, says that UV rays can cause cataracts and macular degeneration. That is why sunglass protection is important.

Researchers say that risk is greatest for those in the southern hemisphere, where the UV index is high and lens standards are low. Still, it is better to play it safe.

Yelena Kuzmina, the manager of Fromer Eye Sales Optical, suggests oversized or wrap-around shades for the best protection for your eyes as well as the skin around your eyes.