Acanthamoeba keratitis is a rare but serious infection of the eye. Caused by a microscopic organism called Acanthamoeba (commonly found in water sources, such as tap water, well water, hot tubs, and soil and sewage systems), acanthamoeba keratitis can lead to permanent vision loss or blindness. Symptoms of Acanthamoeba keratitis may include red eyes, eye pain, tearing, light sensitivity, blurred vision, and a feeling that something is in your eye.