Health experts have warned that millions of users of eye lenses around the world could be at the risk of exposing themselves to a virus that can cause blindness.

The bug that is found in dust, sea, showers and swimming pools can reach to eyeballs and cause blindness. The number of people affected by the Acanthamoeba parasite is small worldwide but experts say that the risk is very high.

Fiona Henriquez, of the University of the West of Scotland said that the bug poses a risk to every contact lens wearer in the world. Acanthamoeba feeds on bacteria that are found on dirty contact lenses and cases. When the bug reaches the eyeball, its eats its way and also breeds.

The symptoms of infection include itchy and watery eyes, blurred vision, sensitivity to light, swelling of the upper eyelid and extreme pain, according to the scientists. The patients have to be treated every 20 minutes for three weeks and severe cases require cornea transplants.

Craig Roberts, professor at Strathclyde University has expressed concerns over the risks of the disease. The scientists are now working on a solution to better clean lenses in order to avoid infectious bugs being carried in the lenses.