Reusable contact lenses ‘more than triple the risk of rare eye infection’

Reusable contact lenses more than triple the risk of a rare eye infection, research suggests (Chris Young/PA) (PA File)

Reusable contact lens wearers are nearly four times more likely than daily disposable lens wearers to develop a rare, sight-threatening eye infection, according to a study.

The researchers suggest that people should avoid wearing their lenses while swimming or showering, and that the packaging should include “no water” stickers.

The study identified multiple factors that increase the risk of Acanthamoeba keratitis (AK), including reusing lenses or wearing them overnight or in the shower.

AK is a type of corneal infection and is a condition that causes inflammation of the cornea, the clear, protective outer layer of the eye.

Since approximately 300 million people worldwide wear contact lenses, it is important for people to know how to minimize the risks of developing keratitis.

Professor John Dart, UCL and Moorfields Eye Hospital

The researchers estimate that 30-62% of cases of the condition in the UK, and potentially in many other countries, could be prevented if people switched from reusable lenses to daily disposables.

Lead author Professor John Dart, from the UCL Institute of Ophthalmology and Moorfields Eye Hospital NHS Foundation Trust, said: “In recent years we have seen an increase in Acanthamoeba keratitis in the UK and Europe, and although infection is still rare, preventable, and warrants a public health response.

“Contact lenses are generally very safe, but they are associated with a small risk of microbial keratitis, most commonly caused by bacteria, which is the only sight-threatening complication of contact lens wear.

“Given that approximately 300 million people worldwide wear contact lenses, it is important that people know how to minimize the risks of developing keratitis.”

Researchers say contact lens wear is now the leading cause of microbial keratitis in healthy-eyed patients in countries of the global north.

While vision loss as a result of microbial keratitis is uncommon, Acanthamoeba, while a rare cause, is one of the most serious.

It is responsible for about half of contact lens wearers who develop vision loss after keratitis.

Around 90% of AK cases are associated with avoidable risks, although the infection remains rare, affecting fewer than one in 20,000 contact lens wearers in the UK each year.

The most severely affected patients, a quarter of all, lose less than 25% of their vision or go blind after the disease and face prolonged treatment.

Overall, 25% of affected people require corneal transplants to treat the disease or restore vision, the study suggests.

The study, led by researchers from UCL and Moorfields, recruited more than 200 Moorfields Eye Hospital patients who completed a survey, including 83 people with AK.

They were with 122 people who came to eye clinics with other conditions.

The study found that people who wore reusable soft contact lenses (such as monthly ones) were 3.8 times more likely to develop AK, compared to people who wore daily disposable lenses.

Showering with lenses increased the odds of AK by 3.3-fold, while wearing lenses at night increased the odds by 3.9-fold.

Among daily disposable wearers, reusing their lenses increased the risk of infection, while a recent contact lens review with a healthcare professional lowered the risk.

First author, Associate Professor Nicole Carnt, from UNSW Sydney, UCL Institute of Ophthalmology and Moorfields Eye Hospital, said: “Previous studies have linked AK to contact lens wear in hot tubs, swimming pools or lakes, and here we’ve added showers to that list, stressing that exposure to water should be avoided when wearing lenses.

“Public swimming pools and coastal authorities could help reduce this risk by advising against swimming with contact lenses.”

Professor Dart added: “Contact lens packaging should include information about lens safety and risk prevention, even as simple as ‘no water’ stickers on each case, particularly as many people buy their lenses online without talking to a health professional.

“Basic contact lens hygiene measures can go a long way in preventing infection, such as thoroughly washing and drying your hands before inserting your lenses.”

The study, published in Ophthalmology, was funded by Fight for Sight, the NIHR Moorfields Biomedical Research Center, and the Moorfields Eye Charity.

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