Rapid diagnosis of Acanthamoeba keratitis using calcofluor white.

Calcofluor white (CFW) is a chemofluorescent dye with an affinity for the polysaccharide polymers of amebic cysts. Using CFW staining with fluorescent microscopy, we demonstrated amebic cysts in corneal scrapings and keratectomy specimens from four patients with culture-proved Acanthamoeba keratitis and from one in whom CFW was the only positive laboratory test. Calcofluor white staining is simple, rapid, and highly reliable in the diagnosis of Acanthamoeba keratitis.