8. Acanthamoeba Keratitis

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This is why contact lens wearers should never rinse their lenses in anything but the specially-prepared fluid made for that purpose. While most of us probably remember the amoeba as that harmless-looking microscopic blobby-looking critter we viewed under a microscope in high school science class, this amoeba is not one you want to be hanging out with. It is sometimes found in tap water and can invade the eye causing vision problem or even blindness.