Swimming in Contact Lenses Can Cause Vision Loss—Here's How

If you've been swimming a lot this summer and you don't have perfect vision, you should definitely read this.

Here’s something to keep in mind this summer: Turns out, swimming in your contact lenses is definitely not a good idea.

The warning comes from a new case report in the New England Journal of Medicine, which tells the story of a woman who, after swimming in her contact lenses, developed acanthamoeba keratitis, an infection that can impair your vision.

The patient had her eye examined after two months of intermittent pain, sensitivity to light, and blurry vision in her left eye. (FYI: The patient’s eye looks green in this photo because of fluorescein eye stain, which helps doctors detect foreign bodies in the eye and damage to the cornea, according to the U.S. National Library of Medicine.)

The woman’s condition, acanthamoeba keratitis, is relatively rare, but it’s not necessarily unheard of. “This is not a common condition, but most busy eye clinics will see five to 10 cases a year,” Douglas Fredrick, MD, chief of pediatric ophthalmology for the Mount Sinai Health System in New York City, tells Health.

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Dr. Fredrick says you can get an acanthamoeba keratitis infection after swimming in any water: lakes, pools, hot tubs—they’re all fair game, and he describes the parasite that causes the infection as “hearty” but says it’s more common in warm water. But here’s the thing: It won’t cause problems for you unless it attaches to your contact and causes an infection, he says. So swimming in waters where the parasite lives isn’t necessarily dangerous—unless you have contact lenses in.

For this reason, all contact lens manufacturers recommend that you don’t swim in your contacts, Dr. Fredrick says. Even a “well-maintained pool can have the organism” that causes the infection, he adds.

Acanthamoeba keratitis doesn’t always go away with a quick fix. “It’s very difficult to treat. It requires use of topical eye drops that have to be used hourly for weeks at a time,” Dr. Fredrick explains. He says that in some cases patients have to use them for months. Sometimes, patients have to undergo a cornea transplant after using the drops. This is because the infection can cause corneal scarring. The patient featured in the new report had to have a transplant. Even after that, her vision wasn’t all the way restored; it was 20/80. (For reference, anything worse than 20/70 is considered “low vision” according to the American Foundation for the Blind.)

Your best bet? Ditching the lenses when you swim. “The safest thing would be to never swim with [contact lenses],” Dr. Fredrick says. But, luckily, you don’t have to risk impaired sight to go for a dip. “You can buy a pair of prescription goggles for about $20,” Dr Fredrick says. He adds that when you consider the possible alternative—vision loss—“that investment is far better.”

Sure, you might not get a perfect tan wearing goggles—but that’s definitely a better problem than losing your eyesight after going for a swim.

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