It's late, you're tired, and the last thing you want to do is get out of bed and take out your contact lenses. If so, you're not alone: Around one-third of people who wear contact lenses have reported that they sleep or nap in them.
But people who do this have six to eight times the risk of developing eye infections, according to a new report published today (Aug. 16) in the Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report.
"Among the many behaviors that increase the risk for a contact lens-related corneal infection, sleeping in lenses is one of the riskiest and one of the most commonly reported behaviors among adolescent and adult contact lens wearers," the researchers wrote in the study. ['Eye' Can't Look: 9 Eyeball Injuries That Will Make You Squirm]
These infections, called microbial keratitis, are more common in people who wear contact lenses; the infections are caused by bacteria or other microbes infecting the eye's cornea, according to the report.
(The CDC noted that it receives funding from the Contact Lens Institute to support the agency’s Healthy Contact Lens Program. The Contact Lens Institute played no role in this report, the researchers said.)
The researchers presented six cases of patients who slept in their contact lenses and developed keratitis. Some of the infections resulted in corneal damage, permanent vision loss and the need for surgery. One case involved a 34-year-old man who was sleeping with contact lenses three to four nights a week and also swimming in them.
He went to the doctor with a blurry and red left eye. He was treated for bacterial and fungal microbial keratitis for a couple months, but his symptoms didn't improve. It turns out he contracted a very rare infection called Acanthamoeba keratitis, which is caused by an amoeba, a single-celled organism, according to the CDC. Though the infection resolved with new treatment, the man did have some vision loss and had to switch to rigid contact lenses.
In another case, a 17-year-old woman slept in over-the-counter soft contact lenses and developed a Pseudomonas aeruginosa bacterial infection, which caused an ulcer in her right cornea. With eye drops, the infection cleared up, but her corneal fibers were permanently scarred.
A 59-year-old man heard a popping sound in the shower and felt pain in his left eye. He had recently worn his soft contact lenses overnight on a two-day hunting trip. It turns out he had a large perforated ulcer in his cornea and needed a corneal transplant. He recovered some vision, which improved after a cataract surgery.
All of the six patients required eye drops, while two required surgery, and most had permanent eye damage or vision loss, according to the report.
But these cases may not be representative of the typical infections associated with contact lenses. Rather, these cases were chosen by ophthalmologists, who can perform eye surgery and thus could have specifically chosen more-extreme cases, the report said. Also, these patients may have been susceptible to infections, and "other contact lens wearers with the same habits might be able to sleep in lenses without adverse outcomes," the authors wrote.
However, sleeping, even occasionally, in contact lenses does increase the risk of infection regardless of lens material and frequency, according to the report.
Some lenses are approved by the Food and Drug Administration (FDA) for overnight wear, but even those are associated with an increased risk for infection when worn overnight, according to the report. These overnight-wear lenses are considered class 3 medical devices, those that have the greatest risk of harm. This class includes implantable pacemakers.
"Contact lens wearers can take simple steps to prevent contact lens-related eye complications, such as talking to their doctors about not sleeping or swimming in lenses, and replacing lenses and storage cases when recommended," the CDC wrote in a statement about the report.
Originally published on Live Science.
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Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.