Reusable Contact Lenses May Increase Risk of Rare, Sight-Threatening Eye Infection

People who wear reusable contact lenses may have an increased risk of developing a rare but serious eye infection, new research shows.

Acanthamoeba keratitis (AK)—an infection in the outer covering of the eye, called the cornea—is nearly four times more likely to occur in people who wear reusable contact lenses, compared to people who change their contact lenses daily, according to a recent study published in Ophthalmology.

"In recent years we have seen an increase of Acanthamoeba keratitis in the UK and Europe, and while the infection is still rare, it is preventable and warrants a public health response," lead author John Dart, MA, DM, of University College London's (UCL) Institute of Ophthalmology and Moorfields Eye Hospital NHS Foundation Trust, told Health in an email.

According to Dart, with more than 300 million people across the globe who regularly wear contact lenses, it's essential to educate people on the risks of contact lens use, and how to wear and care for them properly, to prevent such infections.

Reusable Contact Lenses Linked to Increased Risk of Eye Infection

For the study, researchers from University College London and Moorfields Eye Hospital, recruited over 200 patients—83 people with AK, and 122 patients with other eye conditions—to complete a survey about their contact lens usage.

Patients who wore reusable soft contact lenses—like those meant to be changed on a monthly basis—were 3.8 times more likely to develop AK than those who wore daily disposable contact lenses.

According to Dart, 30%–62% of cases of AK could be prevented in the U.K.—and potentially even other countries not in the study—if people just switched from reusable contact lenses to daily disposable ones.

In addition to the type of contact lenses worn, certain behaviors also increased a person's odds of AK: Showering with contact lenses increased the odds of AK by 3.3 times, and wearing contact lenses overnight increased the risk by 3.9 times.

"We also found that, for those using daily disposable lenses, reusing the lenses (usually involves storing them in water or solution overnight to prevent their drying out) increased the risk [of AK] by 5.4 fold," said Dart.

Although contact lenses have been known to be a strong risk factor for AK, eye doctors say this study further raises awareness about the infection—and adds more data to back up daily disposable contact lenses as the preferred option.

"The main finding that is new here is that patients who are wearing daily disposable contact lenses have a lower risk of developing AK compared to patients who are wearing other forms of soft contact lenses, the ones that you keep for a month or so," Uri Soiberman, MD, assistant professor of Ophthalmology at Johns Hopkins Medicine, told Health. "The study raises awareness for the role of smart and responsible contact lens wear and the importance of hygiene."

Acanthamoeba Keratitis, Explained

An AK infection is caused by a microscopic organism called Acanthamoeba, commonly found in bodies of water, as well as in soil and air. When Acanthamoeba infects the eye's cornea—the transparent layer that covers the eye—it's known as AK.

Contact lenses predispose patients to AK because contact lenses, to some degree, cause microtrauma to the surface of the eye, according to Dr. Soiberman.

"The surface of the eye has a very important role in barrier function and maintaining the eye from pathogens, bacteria, fungus, and other organisms such as Acanthamoeba," said Dr. Soiberman. "Once that barrier function is damaged by micro-abrasions from contact lenses, then there's a higher risk of developing infections."

For the most part, poor hygiene habits when it comes to contact lenses—especially reusable ones—increase the risk of AK.

"People who wear [reusable lenses] are more likely to wear them more often, sleep with the lenses [in], and not clean them as well," Daniel Laroche, MD, a glaucoma specialist in New York and a clinical assistant professor of Ophthalmology with the Icahn School of Medicine at Mount Sinai Medical Center, told Health. "This can weaken the natural corneal barriers and increase the chance of contamination and infection."

Contact lens cases for reusable lenses may also add to AK risk. "About 3%–5% of healthy lens users will have Acanthamoeba in their lens cases," said Dart. "The Acanthamoeba comes from the water supply where it is present in low levels."

Swimming or showering with lenses in, inserting them with wet hands, and even washing your face with lenses still in can also increase the risk of AK.

Though rare, AK is a serious infection that can look like other eye infections. Symptoms can last for several weeks to months, and can include:

• Eye pain
• Eye redness
• Blurred vision
• Sensitivity to light
• Sensation of something in the eye
• Excessive tearing

If AK is caught earlier, it can be treated effectively, said Dr. Laroche. "If too late then one can lose their cornea and require a corneal transplant," he added. In some cases, untreated AK can result in possible vision loss or blindness.

Preventing Acanthamoeba Keratitis in Contact Lens Wearers

Ideally, "daily disposable contacts are always preferred," said Dr. Laroche—but they may not be an available option to everyone who needs sight correction.

"[People] with high astigmatism or who need very strong long- or short-sight prescriptions," may not be able to get dailies, said Dart. Daily use contact lenses may also be more expensive compared to longer-lasting reusable ones, added Dr. Soiberman.

Whichever option you end up using, it's important to understand the risks and benefits of using contact lenses, how to safely and effectively use them, and to pay attention to any eye health issues that may arise after use.

To further reduce your risk of AK, the CDC recommends taking the following steps to ensure your contact lenses—regardless of how often you're supposed to replace them—stay safe and clean:

• Visit an eyecare provider for regular eye exams
• Wear and replace contact lenses according to the prescribed and manufacturer's instructions
• Remove contact lenses before any water-based activity (showering, swimming, washing your face)
• Thoroughly wash and dry hands before inserting or removing contact lenses
• Always cleanse and store lenses with fresh solution
• Opt for a multipurpose solution to clean, rinse, disinfect, and store lenses—do not use saline or rewetting drops for cleansing
• Properly clean and store contact lens cases when not in use
• Replace contact lens cases every three months

"Contact lenses are a great tool," said Dr. Soiberman, "but if you don't use them correctly, you may predispose yourself to corneal disease and potentially blindness."