Reusable contact lenses more than triple risk of preventable rare eye infection

People who wear reusable contact lenses are almost four times more likely than those who wear daily disposable lenses to develop a rare sight-threatening eye infection, according to a study by researchers from UCL and Moorfields.

The case-control study published in Ophthalmologyidentifies several 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 microbial keratitis (corneal infection) – a condition that results in inflammation of the cornea (the transparent protective outer layer of the eye).

Lead author Professor John Dart (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 the infection is still rare, it is preventable and warrants a public health response.

Contact lenses are generally very safe but are associated with a low risk of microbial keratitis, most often caused by bacteria, which is the only sight-threatening complication of their use. Given that approximately 300 million people around the world wear contact lenses, it’s important that people know how to minimize their risk of developing keratitis.”

Contact lens use is now the leading cause of microbial keratitis in patients with otherwise healthy eyes in northern countries. Loss of sight resulting from microbial keratitis is rare but Acanthamoeba, although a rare cause, is one of the most serious and is responsible for approximately half of contact lens wearers who develop vision loss after keratitis. 90% of AK cases are associated with preventable risks, although the infection remains rare, affecting less than 1 in 20,000 contact lens wearers per year in the UK.

AK causes pain and inflammation in the front of the eye, the cornea, due to infection with Acanthamoeba, a cyst-forming microorganism. The most severely affected patients (a quarter of the total) end up with less than 25% vision or become blind as a result of the disease and face prolonged treatment. Overall, 25% of those affected require a corneal transplant to treat the disease or restore vision.

For the study, researchers recruited more than 200 patients from Moorfields Eye Hospital who responded to a survey, including 83 people with AK, and compared them to 122 participants who came to eye care clinics with other conditions. , which acted as a control group.

People who wore reusable soft contact lenses (such as monthly lenses) were 3.8 times more likely to develop AK, compared to people who wore daily disposable lenses. Showering with lenses increased the odds of KA by 3.3 times, while wearing lenses overnight increased the odds by 3.9 times. Among daily disposable wearers, reusing their lenses increased their risk of infection. Having recently had contact lenses checked by a medical professional reduced the risk.

After further analysis, researchers estimated that 30-62% of cases in the UK, and potentially many other countries, could be prevented if people switched from reusable lenses to daily disposable lenses.

A recent study led by Professor Dart found that the prevalence of AK is increasing in the UK. Looking at incidence data from Moorfields Eye Hospital from 1985 to 2016, he and his team found an increase from 2000-2003, when there were eight to 10 cases per year, to between 36 and 65 cases. annually at the end of the study period. .

First author, Associate Professor Nicole Carnt (UNSW, Sydney, UCL Institute of Ophthalmology and Moorfields Eye Hospital) said: “Previous studies have linked AK to contact lens wear in spas, swimming pools or lakes, and here we added showers to that. list, emphasizing that exposure to water while wearing contact lenses should be avoided. 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 on lens safety and risk prevention, even as simple as ‘water-free’ stickers on each case, especially since many people buy their lenses online without talking to a healthcare professional.

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

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

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