A new study led by researchers from University College London (UCL) and Moorfields Eye Hospital has shown that people who make use of reusable contact lenses are at a nearly four times higher risk of developing a rare, vision-threatening eye infection, compared to those who use disposable contacts.
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Contact Lenses
Contact lenses are mostly safe. But there is a slight risk of their use resulting in infection by bacteria that could cause sight complications.
In this research published in the journal Ophthalmology, scientists pinpointed several factors that predispose people to Acanthamoeba keratitis (AK). Among these factors were contact lens reuse, overnight wearing, and wearing in the shower.
“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,” said lead author Professor John Dart of the UCL Institute of Ophthalmology and Moorfields Eye Hospital NHS Foundation Trust.
This research calls for contact lens wearers to be more careful to reduce their risk of sight-threatening eye infections.
The threat of Acanthamoeba keratitis
AK is a rare and preventable corneal infection. It is a form of microbial keratitis that is characterized by inflammation of the cornea, the outer protective layer of the eye.
The cyst-forming, tiny organism called Acanthamoeba causes AK. An infection of the cornea causes it to become inflamed and painful.
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As per researchers, people who are most affected by this condition (around a quarter of all patients) have lower than 25 percent of normal vision capability. Some severe cases lead to complete blindness. Extended treatment or corneal transplants are usually required to correct the disorder or restore sight.
With roughly 300 million people said to use contact lenses globally, researchers say the use of this type of eyewear is now the primary cause of microbial keratitis in otherwise healthy individuals in the global north.
Vision loss from microbial keratitis is still rare. But Acanthamoeba accounts for around 50 percent of sight loss cases among contact lens wearers that develop keratitis.
As high as 90 percent of AK cases result from avoidable risk factors, according to researchers.
Higher risk of eye infection
Researchers observed in a recent study, also led by Dart, a rising trend in AK incidence in the UK. The team noted an increase in cases beginning from 2000-2003 after analyzing incidence data for 1985 to 2016 from Moorfields. Annual cases rose from eight to 10 in 2000-2003 to between 36 and 65 at the end of the period covered in the study.
The research team in the current study enrolled more than 200 Moorfields patients, 83 of whom have AK. The control group consisted of 122 people who visited eye clinics for other complaints. These subjects were asked to complete a survey.
Dart and his colleagues observed a 3.8 times higher risk of having AK among patients using reusable contact lenses, compared to those who use daily disposable ones. People who used disposable contacts also increased their risk of eye infection by reusing their lenses.
The risk of having an eye infection was even greater among those who wore their contacts overnight, at 3.9 times. Having a shower with the eyewear on was found to increase AK risk by 3.3 times.
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“Previous studies have linked AK to wearing contact lenses in hot tubs, swimming pools, or lakes, and here we have added showers to that list, underlining that exposure to any water when wearing lenses should be avoided,” said Associate Professor Nicole Carnt, the first author of the study. “Public pools and coastal authorities could help reduce this risk by advising against swimming in contact lenses.”
Further analysis by the research team revealed that up to 62 percent of AK cases in the UK, and possibly in other places, could be averted by using daily disposable contacts.
Dart suggested including lens safety information in packaging, even if it’s only a “no water” sticker to lessen risks. Basic hygiene measures, such as careful washing and drying of hands before handing lenses, could help a lot as well.
References
Acanthamoeba Keratitis Risk Factors for Daily Wear Contact Lens Users
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