With the Acanthamoeba parasite also found in dust, sea, showers and swimming pools, millions of people are at risk of going blind worldwide. The actual number of infections is small but treatment is long, painful and not completely effective.
"It is a potential problem for every single contact lens wearer," the Daily Mail quoted Fiona Henriquez, of the University of the West of Scotland, as saying.
Acanthamoeba, a tiny single-celled parasite, feeds on bacteria found on dirty contact lenses and cases. When the lens is put in the eye, it starts to eat its way through the cornea and breeds as it goes.
Symptoms are itchy and watery eyes, blurred vision, sensitivity to light, swelling of the upper eyelid and extreme pain. According to an optician, vision can be permanently damaged within a week. Treatment includes Dettol-like eye drops, with patients initially being treated every 20 minutes, and spending three weeks in hospital. The most severe cases are given cornea transplants.