Eye parasite can be avoided with good contact lens hygiene

[October 09, 2018]  By Carolyn Crist

(Reuters Health) - UK researchers have confirmed an uptick in cases of Acanthamoeba keratitis, an eye infection that most often affects contact lens wearers.

Contact lens users can avoid the severe infection by washing and drying their hands when they handle their contacts, storing the lenses in clean solution daily rather than in water or old solution, and as much as possible, avoiding wearing lenses while swimming or bathing.

"We think the condition is 90 percent preventable if water exposure is avoided and effective lens solution is used properly or disposable contact lenses are used," said senior study author Dr. John Dart of University College London and Moorfields Eye Hospital.

Not all lens solutions are effective, and ingredient and risk information isn't often easily accessible on product packages or manufacturer websites, Dart noted

"The way the solution is formulated can sometimes cause the problem, too, but users can't find this easily," Dart told Reuters Health in a phone interview.

Acanthamoeba organisms are present in the air, soil, dust and water. At least half of the population has antibodies to the organisms, indicating they've been exposed, the study team writes in the British Journal of Ophthalmology.

Acanthamoeba keratitis is still quite rare. Nevertheless, the cyst-forming amoeba can be difficult to treat, leading to chronic infection that affects contact lens users for years. The most severely affected patients in the UK, for example, required nearly a year of treatment, more than three years of follow-up, dozens of hospital visits and had poor vision after the infection resolved, the study team notes. Some patients needed corneal transplants.

To see if infections are increasing, Dart and colleagues looked at data on Acanthamoeba cases at Moorfields between 1984 and 2016. The hospital treated 75 percent of cases in southeast England and 35 percent of all UK cases during that period, so it is likely representative of what's happening across the country.

The researchers also studied surveys completed by contact lens users in Moorfields' Accident and Emergency Department, including people who had Acanthamoeba keratitis or other eye disorders.

The research team found that the current outbreak started in 2010, when incidence of the condition rose to about 50 cases per year. That represented a threefold increase compared with 2004-2009.

When they looked at factors associated with infection, researchers found that users of contact lens solution containing the ingredient Oxipol - which has since been phased out by its manufacturer - were nearly five times more likely to contract the infection.

Deficient hand-washing and engaging in water activities like swimming and showering while wearing contact lenses were also tied to risk of infection.

The outbreak has been less severe in the U.S. and Australia, but eye experts are still watching potential developments. After an outbreak in the U.S. in 2007, for instance, cases rose 17-fold.

"Out of that work, it hit home for us that people had not-so-great habits," said Dr. Jennifer Cope of the U.S. Centers for Disease Control and Prevention in Atlanta, Georgia, who wasn't involved in the UK study.

"Contact lens wearers weren't aware, but quick shortcuts were putting them at risk for infections," she said in a phone interview. "We're now focusing on prevention and communication about the best hygiene."

Cope and colleagues have found that some lens wearers "top off" their contact lens cases with new solution, rather than using entirely new solution daily.

"The solution in the case sits overnight and loses its disinfectant capabilities," she said. "This seems benign, but 'topping off' basically dilutes fresh solution and makes it ineffective."

Although most manufacturers test their solutions for activity against Acanthamoeba, it's not mandatory, and results can change once products are shipped and stored. Ultimately, consumers should try to make the best shopping decisions possible and practice good hygiene at home, Dart said.

"Overall, contact lens wearers should avoid contaminating their contacts with tap water," he added. "Use a solution that has been on the market for some time and is known to be safe."

SOURCE: https://bit.ly/2Ni91kN British Journal of Ophthalmology, online September 19, 2018.

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