• Acanthamoeba keratitis is a difficult diagnosis to make with routine stains and cultures. Gram's, Giemsa, and hematoxylin-eosin stains do not differentially stain Acanthamoeba, making the detection of organisms difficult. Trophozoite and cyst forms in paraffin-embedded corneal tissue sections can be rapidly and differentially stained with calcofluor white. Under the fluorescence microscope, the trophozoites are bright red-orange, and cyst cell walls fluoresce bright apple-green with red-orange cytoplasm. Retrospective identification can be made by destaining hematoxylin-eosin-stained sections. Digesting background corneal tissue with trypsin or collagenase and hyaluronidase solutions helps to more readily identify trophozoites.
Silvany RE, Luckenbach MW, Moore MB. The Rapid Detection of Acanthamoeba in Paraffin-Embedded Sections of Corneal Tissue With Calcofluor White. Arch Ophthalmol. 1987;105(10):1366-1367. doi:10.1001/archopht.1987.01060100068028