PEOPLE who use reusable contact lenses are four times as likely as those wearing daily disposables to develop a sight-threatening eye infection.
British researchers have suggested people should avoid wearing their lenses while swimming or in the shower.
The study, which was published in Ophthalmology found that reusing lenses, wearing them overnight or in the shower increased a person’s risk of Acanthamoeba keratitis (AK).
AK is an infection of the cornea – the clear outer layer of the eye.
The condition happens when the parasite acanthamoeba gets trapped between the cornea and the contact lens.
It eats into the cornea, causing severe pain and in a quarter of cases, blindness.
Researchers from University College London and Moorfields Eye Hospital estimate that 30-62 per cent of UK cases of the condition could be prevented if people switched from reusable to daily lenses.
They also called for manufacturers to include “no water” stickers on lens packaging.
Lead author Professor John Dart, of UCL, said: “In recent years we have seen an increase of Acanthamoeba keratitis in the UK and Europe.
“While the infection is still rare, it is preventable and warrants a public health response,” he said.
According to the professor, contact lenses are “generally very safe” and the risk of AK is small.
AK is the only sight-threatening complication of contact lens 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,” he explained.
Researchers say contact lens use is now the leading cause of AK in patients with otherwise healthy eyes in countries in the global north.
Some 90 per cent of AK cases are associated with avoidable risks, although the infection remains rare.
AK affects fewer than one in 20,000 contact lens wearers per year in the UK.
What are the signs and symptoms of the eye infection?
An infection in your eye can show up in many different ways. A lot depends on which part of your eye has the problem. Symptoms can include:
- sensitivity to light and excessive tearing
- blurred vision with eye redness and pain
- sensations of having something in your eye
- severe headaches
Overall, 25 per cent of people affected by the infection require corneal transplants to treat the disease or restore vision, the study suggests.
As part of the study, the researchers recruited more than 200 patients of Moorfields Eye Hospital who completed a survey, including 83 people with AK.
They were with 122 people who came to eyecare clinics with other conditions.
The study found that people who wore reusable soft contact lenses (such as monthlies) had 3.8 times the odds of developing AK, compared to people who wore daily disposable lenses.
Showering with lenses increased the odds of AK by 3.3 times while wearing lenses overnight increased the odds by 3.9 times.
Among daily disposable wearers, reusing their lenses increased their infection risk while a recent contact lens check with a health professional reduced the risk.