People who wear reusable contact lenses are nearly four times as likely as those wearing daily disposables to develop a rare sight-threatening eye infection, finds a study led by UCL and Moorfields researchers.
The case control study, published in Ophthalmology, identifies multiple factors that increase the risk of Acanthamoeba keratitis (AK), including reusing lenses or wearing them overnight or in the shower.
AK is one type of microbial keratitis (corneal infection) — a condition that results in inflammation of the cornea (the eye’s clear protective outer layer).
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 of Acanthamoeba keratitis in the UK and Europe, and while 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 small risk of microbial keratitis, most commonly caused by bacteria, and which is the only sight threatening complication of their use. Given that an estimated 300 million people across the globe wear contact lenses, it is important that people know how to minimise their risks for developing keratitis.”
Contact lens use is now the leading cause of microbial keratitis in patients with otherwise healthy eyes in countries in the global north. Sight loss resulting from microbial keratitis is uncommon but Acanthamoeba, although a rare cause, is one of the most severe and is responsible for about half of those contact lens users who develop sight loss after keratitis. 90% of AK cases are associated with avoidable risks, although the infection remains rare, affecting fewer than 1 in 20,000 contact lens wearers per year in the UK.
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