When was the last time you replaced your sunglasses? If it’s been a while you may want to go shopping for a new pair of shades. UV protection on sunglasses can deteriorate over time, leaving your eyes at risk for major problems.

The sun’s damaging rays can make your eyes vulnerable to cataracts, a clouding of the eye’s lens and macular degeneration, the leading cause of blindness.

McLaughlin on Your Side took a bag full of old sunglasses to a local optometrist’s office to test just how effective older shades are at protecting your eyes.

“We've got these old sunglasses, 10 of them. We want to see if they're still good," explained McLaughlin as he showed the pairs of shades to optometrist Harbir Sian.

Sian used two transmission meter machines, one to test how much of the dangerous light spectrum the sunglasses block out and the other to test how many UV rays were getting through.

All the sunglasses scored well the spectrum test. That means they were operating as designed to block the spectrum, but many lost their ability fully block UV light.

“There’s 11 per cent getting through on both sides,” Sian said as he tested a 20-year old pair of aviator sunglasses.

Other shades let through two to six per cent of UV light. Sian says you want more protection than that.

"The standard's just become 99.9 per cent," he explained, “and fair skin and light eyes always put you at a little bit higher risk for changes due to UV light exposure."

Seven out of the 10 sunglasses we tested failed.

It’s not how much you pay either. New, cheap sunglasses from the dollar store passed both tests with a score of 100 per cent.

Just beware of cheaper glasses which often have sprayed on coatings that can scratch off over time.

Sian says size is also important. Bigger lenses offer better coverage. Polarized lenses don’t offer more protection, but they do cut down on glare.

“We recommend updating your glasses every couple years to make sure you always have the 100 per cent U.V. blockage," Sian said.

If you want to see how well your sunglasses are holding up, you can walk into almost any optical shop or optometrist’s office and they’ll test your shades for free.