In the United States, it is nearly always associated with contact lens use, as Acanthamoeba can survive in the space between the lens and the eye. For this reason, contact lenses must be properly disinfected before wearing, and should be removed when swimming or surfing.
However, elsewhere in the world, many cases of Acanthamoeba present in non-contact lens wearers.
To detect Acanthamoeba on a contact lens in a laboratory, the contact lens is placed on a non-nutrient agar saline plate seeded with a gram-negative bacteria such as E. coli. If Acanthamoeba are present, they will reproduce readily and become visible on the plate under 10-20X objective on an inverted microscope. Polymerase chain reaction can also be used to confirm a diagnosis of Acanthamoeba keratitis, especially when contact lenses are not involved. Acanthameoba is also characterized by a brawny edema and hazy view into the anterior chamber. Late stages of the disease also produces a ring shaped corneal ulcer.
Signs and symptoms include severe pain, severe keratitis (similar to stromalherpetic disease), corneal perineuritis, and ring ulcer (late in the disease process).
^JOHN D.T. (1993) Opportunistically pathogenic free-living amebae. In: J.P. Kreier and J.R. Baker (Eds.), Parasitic Protozoa. Vol. 3. Academic Press, New York, pp. 143–246.
^Badenoch, PR; Adams M; Coster DJ (February 1995). "Corneal virulence, cytopathic effect on human keratocytes and genetic characterization of Acanthamoeba". International Journal for Parasitology25 (2): 229–39. doi:10.1016/0020-7519(94)00075-Y. PMID7622330.|accessdate= requires |url= (help)