People who don't regularly clean their contact lenses. Are more likely to go blind. A serious eye infection called Acanthamoeba Keratitis. Affects one in 50,000 contact lens wearers. It's caused by a flash-eating parasite called Acanthamoeba. The parasite invades and destroys the cornea of the eye. Leading to a permanent visual impairment or blindness.
The parasite is commonly found in tap water, rivers and soil. Cleaning your lenses in tap water increases the risk of infection. Swimming, showering, bathing or sleeping while wearing your lenses. Also increses the risk of infection.