Contact lens wearers have been urged to look after their eyes following an outbreak of a rare infection which can cause blindness.
Moorfields Eye Hospital in London has seen a rise in the number of cases of Acanthamoeba keratitis since 2011.
The preventable infection causes the front surface of the eye, the cornea, to become painful and inflamed and contact lens wearers are most at risk.
Between 2000 and 2003, eight to 10 cases per year were recorded at the hospital, according to a study published in the British Journal of Ophthalmology.
This rose to as many as 65 cases annually from 2011 to 2016.
A study in 2002 estimated the prevalence of Acanthamoeba keratitis in south east England to be 2.5 cases per 100,000 contact lens wearers, but it is currently two to three times higher, researchers from University College London (UCL) and Moorfields Eye Hospital said.
The most severely affected patients are left with less than 25% of their vision or become blind after having the disease.
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, a cyst-forming microorganism, is found in high levels in UK domestic water supplies.
Reusable contact lens wearers with the eye infection are more likely to have used ineffective contact lens solution, have contaminated their lenses with water or to have reported poor hygiene habits, the researchers said.
Showering, swimming and using hot tubs while wearing contact lenses was also a risk factor.
Prof 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.’