Millions of contact lens users are at the mercy of a bug that is found in tap water and nibbles through the eyeballs causing blindness,scientists have warned.
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,which is the outer layer of the eyeball and breeding as it goes.
Symptoms include itchy and watery eyes,blurred vision,sensitivity to light,swelling of the upper eyelid and extreme pain.
According to Graeme Stevenson,an optician,vision can be permanently damaged within a week.
Generally it leaves you with scarring. Your cornea is your window on life and if the infection penetrates in towards the third layer you are left with scarring,with a kind of frosty windscreen, Stevenson said.
Treatment includes Dettol-like eye drops,with patients initially being treated every 20 minutes,day and night and spending up to three weeks in hospital. The most severe cases are given cornea transplants.
Advice for avoiding the bug includes keeping lenses and cases clean and replacing them regularly.
The findings were presented at the British Science Festival in Aberdeen.