Moorfields Eye Hospital in London says it has seen a rise in the number of cases of Acanthamoeba keratitis since 2011.
The preventable infection causes the cornea – the front surface of the eye – to become painful and inflamed, with contact lens wearers most at risk.
Severely affected patients are sometimes left with less than 25% of their vision, or even become blind.
Just eight to 10 cases a year were recorded at the hospital between 2000 and 2003, but this rose to 35 to 65 cases a year between 2011 and 2016.
Lead author Professor John Dart, from the UCL Institute of Ophthalmology and Moorfields Eye Hospital, said: “This increase in cases highlights the need for contact lens users to be aware of the risks.”
Acanthamoeba is a cyst-forming microorganism that is found in high levels in UK domestic water supplies.
Reusable contact lens wearers with the infection are more likely to have used an ineffective contact lens solution, have contaminated their lenses with water, or have poor hygiene habits.
Professor Dart said: “People who wear reusable contact lenses need to make sure they thoroughly wash and dry their hands before handling contact lenses, and avoid wearing them while swimming, face washing or bathing.
“Daily disposable lenses, which eliminate the need for contact lens cases or solutions, may be safer and we are currently analysing our data to establish the risk factors for these.”
Irenie Ekkeshis, part of Acanthamoeba Keratitis Patient Support Group UK, said: “It is absolutely imperative that regulators and those working in the optical sector take the findings seriously, and use the recommendations to take immediate and urgent action on prevention.
“Contact lenses are medical devices and should be supplied with warnings regarding safe use.”