140 million people wear contact lenses globally. Acanthamoeba keratitis is a nasty infection of the eye that can cause vision impairment or blindness. The culprit is the Acanthamoeba amoebae (single-celled organisms) which invades the cornea. The infection is often associated with use of soft contact lenses. While the condition is rare, it is of concern because its incidence is growing globally and causes significant sight loss in about half of cases. A new study from research in Australia and overseas has found there are a variety of risk factors for contact lens users.
This was a case-control study, which means that people were recruited as they developed the infection and similar controls were recruited at the same time so researchers could compare the similarities and differences between them with a view to establishing possible risk factors for infection. Cases were both ‘daily wear’ contact lens users (where you can use the same pair of lenses for days or weeks) and ‘daily disposable’ contact lens users (where the lens is used for a short time and disposed of, usually after a day).
The researchers found that reusable contact lenses were linked to higher odds of getting an Acanthamoeba keratitis infection compared to the daily disposables. That was the case regardless of whether the reusable lenses were soft or rigid (two available types of lens). Other factors linked to the infection were length of wearing time (the longer they were worn, the higher the risk), showering while wearing lenses, and overnight wear.
Contact lens users will probably be aware of some of these risk factors and others, including the importance of not swimming in contact lenses or wearing them overnight. But the researchers say the shower risk factor is a new one, and that much of the burden of infection can be reduced by encouraging users to wear daily disposables and practice proper contact lens hygiene.
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