According to new research, the risk of contracting a rare eye-threatening eye infection increases nearly four times for reusable contact lens users compared to those who wear daily contact lenses.
Acanthamoeba keratitis (AK) is a type of corneal infection and is a condition that leads to inflammation of the cornea — the clear protective outer layer of the eye.
The study – led by UCL Institute of Ophthalmology and Moorfields Eye Hospital NHS Foundation Trust – identified several factors that increased the risk of AK, including reusing lenses or wearing them at night or in the shower.
More than 200 of the hospital’s patients completed a survey, including 83 people with AK and 122 who visited eye clinics with other conditions.
Researchers found that people who wore reusable soft contact lenses — such as monthly contact lenses — were 3.8 times more likely to develop AK, compared to people who wore daily contact lenses.
Showering with contact lenses increased the risk of AK by 3.3 times, while wearing contact lenses at night increased the risk by 3.9 times.
Researchers estimate that 30-62% of cases of the condition in the UK, and possibly many other countries, could be prevented if people switch from reusable to daily disposable contact lenses.
They have suggested that people should not wear their lenses while swimming or showering, and that the packaging should contain “no water” stickers.
While vision loss from the infection is uncommon, Acanthamoeba, although a rare cause, is one of the most serious, accounting for about half of contact lens users who develop vision loss after keratitis.
About 90% of AK cases are associated with avoidable risks, although the infection remains rare, affecting less than one in 20,000 contact lens wearers a year in the UK.
The worst affected patients – a quarter of the total – get less than 25% of vision or go blind.
Overall, 25% of affected people need corneal transplants to treat the disease or restore vision, the study suggests.
Lead author Professor John Dart said: “In recent years we have seen an increase in Acanthamoeba keratitis in the UK and Europe, and while the infection is still rare, it is preventable and justifies a public health response.
“Contact lenses are generally very safe, but come with a small risk of microbial keratitis, usually caused by bacteria, which is the only vision-threatening complication of their use.
“Since an estimated 300 million people around the world wear contact lenses, it is important that people know how to minimize their risks for developing keratitis.”
The study, published in Ophthalmology, was funded by Fight for Sight, the NIHR Moorfields Biomedical Research Center and Moorfields Eye Charity.