Taiwanese student Lian Kao, 23, reportedly did not remove her limited-wear, disposable contact lenses for six months straight and even wore them while swimming.
As a result, amoeba got under her lenses and tunnelled through her corneas, causing permanent damage that led to blindness in both eyes. The single-cell bug, called Acanthamoeba, can survive in tap water, swimming pools and hot tubs.
Other bacteria are actually more common, it should be noted, and complete loss of sight is fairly extreme, and scarring that impairs vision partially is not uncommon in situations like this.
Via CBC News for the full article.