It’s estimated that four million Canadians depend on contact lenses to correct their vision. And while they’re considered very safe, if they’re not cared for properly you can have some serious issues.

Thatiana Medina learned that lesson when she scratched her cornea recently.

“I forgot to take off my contact lens before going to bed,” she said.

“Falling asleep with your contacts in is a common problem. It can increase your chances of an eye infection by six to eight times,” explained Jeneen Interlandi, Consumer Reports health editor.

Even just a nap with your contacts in can be risky.

Another safety tip is to never rinse your lenses with tap water. It’s rare but it could contain a vision-threatening parasite.

For the same reason, don’t swim with contacts or wear them in a hot tub unless you are wearing goggles.

Generally, don’t use week- or month-long lenses longer than recommended.

Contacts that you use for just one-day are more expensive, but Consumer Reports says it might be worth it.

“Less handling can help make single-use lenses a bit safer than those you use multiple times,” said Interlandi.

You also won’t have to buy as much disinfecting solution with one-day-only lenses and if you prevent just one infection you’re ahead of the game.

The first sign of trouble with contacts can be redness, pain or irritation. If you experience that, you should immediately stop using the contacts, and see an eye doctor if the problem doesn’t clear up in a day or two.