Contributor: Gordon K. Klintworth
Four species of protozoa [Nosema, Encephalitozoon, Microsporidium, and Vittaforma] are rare cause of infectious keratitis [keratitis - infectious]. In the cornea infection by Encephalitozoon is limited to the corneal epithelium. Infection with Nosema, Microsporidium, and Vittaforma corneae typically involves the corneal lamellae and keratocytes and results in a stromal keratitis [keratitis - stromal]. Other protozoa [Acanthamoeba castellani, Acanthamoeba polyphaga, Acanthamoeba culbertsoni,  Acanthamoeba rhysodes) cause an amebic keratitis [keratitis - amebic].