When You Sleep In Contacts, This Is What Happens To Your Eyes

It's happened before. You were tired in that "I just need to take a nap for a bit" kind of way, but the next thing you know, it's daytime, and you've just spent the night sleeping in street clothes, makeup... and with your contact lenses in.

Sleeping with contacts in is so harmful that in 2016, the U.S. Centers for Disease Control identified it as "risk behavior" that could have serious outcomes, including blindness. It ranked sleeping with lenses in with other risky practices including not visiting an eye doctor annually, failing to replace lens storage cases on a regular basis, and swimming with your lenses in (via CDC).

To understand why sleeping with contacts in is so dangerous, we'd have to understand what our eyes do when we sleep... which some of us may think is nothing, since we're asleep and they are meant to be closed.

When we sleep, that happens to be when our eyes carry out the repair and regenerative work it cannot do when we are awake (via Cooper Vision). To do the work, eyes need ambient oxygen exposure, which is important for keeping your eyes healthy."What a contact lens does is limit the oxygen even more because it creates a barrier between the oxygen and the cornea," Russel Wohl, an eye doctor, tells Glamour.

Inserting a foreign object (because really, that's what a contact lens is) into a part of your body and leaving it there also increases your chances of developing an infection in that area. If bacteria happens to get into your eye and makes its way to your cornea, the contact lens creates the ideal condition for an infection to take root and thrive. "The bacteria can then become opportunistic and literally start to eat away at your cornea," says Wohl. "Worst case scenario from that is loss of vision." There is also the threat of hypoxia, which is when a specific part of a body is deprived of oxygen.

Eye doctors are so wary about having people sleep with contact lenses that they'd think twice about giving their patients a free pass, even if their patients are using extended wear lenses. "I'm more on the conservative side of things," says Wohl, "so even with my extended wear patients, if it isn't too much hassle, I recommend that everyone try to take them out every single day. If you ask me, that's the healthiest option."

If you do get an infection, Cleveland Clinic recommends you save the lenses and take them to your doctor instead of throwing them away, so doctors are able to culture the lenses to identify the cause of your problem.