Daily disposable contact lenses may reduce the risk of Acanthamoeba keratitis

1. In a small case-control study, patients using reusable contact lenses had a 4.14 times higher risk of Acanthamoeba keratitis than those who use daily disposable lenses.

2. Among daily disposable contact lens users, shorter duration per day of contact lens wear, showering with contact lenses, reuse of contact lenses, and wearing lenses overnight were associated with a raise Acanthamoeba risk of keratitis.

Level of evidence assessment: 3 (Average)

Summary of the study: The use of contact lenses increases the risk of microbial keratitis or infection of the surface of the eye. Acanthamoeba is a trophozoite that is a rare cause of contact lens-associated keratitis, but often leads to severe infection and loss of vision. This single-center case-control study aimed to identify risk factors for Acanthamoeba keratitis (AK) in contact lens wearers. About 80 patients diagnosed with AK were compared with about 120 controls. In a model adjusted for compliance with contact lens hygiene and interval between contact lens appointments, subjects who used reusable contact lenses were 4.14 times more likely to have a KA than those who used daily disposable lenses. Rigid gas permeable lenses were also associated with a higher risk of AK than daily disposable lenses. Within the group of daily disposable contact lens users, risk factors for AK were wearing contact lenses for less than 12 hours per day versus 12 hours or more, showering with contact lenses, reuse contact lenses and wearing contact lenses overnight. The interpretation of these results is limited by the small sample size, the design of the case-control studies and the use of a questionnaire subject to reporting bias. Nevertheless, the finding of a significant reduction in the risk of Acanthamoeba keratitis with daily use of disposable contact lenses is consistent with other studies showing benefit over other keratitis-causing organisms and with research showing that lens cases can be a site of colonization by Acanthamoeba. This study therefore represents an argument in favor of daily disposable lenses to reduce the risk of infection.

Click to read the study in Ophthalmology

Relevant reading: Microbial keratitis linked to contact lenses: how epidemiology and genetics have helped us in pathogenesis and prophylaxis

In depth [case-control study]: Patients treated for AK in a single large center in England between 2011 and 2014 were included as cases. AK was diagnosed based on culture data, histopathology, consistent clinical course, and response to treatment, or polymerase chain reaction. Controls were contact lens users presenting to the same emergency department for unrelated diagnoses between 2014 and 2015. Risk factor assessment was based on a questionnaire. Adjusted odds ratios for daily use of disposable versus reusable lenses as well as independent risk factors were calculated using selection and least absolute removal operator models. The adjusted odds ratio of 4.14 for reusable contact lenses versus daily disposable contact lenses in AK patients versus controls had a 95% confidence interval of 1.92 to 8.9 (p

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