Examination of the Contact Lens with Light Microscopy: An Aid in Diagnosis of Acanthamoeba Keratitis

Abstract

The demonstration of amebic cysts on the surface of a patient's hydrophilic contact lens by direct examination with light microscopy can provide rapid confirmation of the diagnosis of acanthamoeba keratitis. This technique is a simple, quick, and noninvasive adjunct to the examination of the corneal scraping. Lenses can be examined unstained or after application of calcofluor white stain. A 48-year-old woman presented with a 3-week history of decreased vision bilaterally and severe ocular pain. Previous treatment with topical antibiotics, corticosteroids, and cycloplegic agents was ineffective. A wearer of Saturn contact lenses, she stored, rinsed, and cleaned her lenses with a commercial unpreserved sterile saline. However, when she developed the symptoms, she had not disinfected her lenses for >1 year. Her visual acuity was 20/300 in the right eye and 20/400 in the left eye. She had bilateral stromal infiltrates of the corneal ring with overlying central epithelial defects, bilateral lid edema, marked ciliary injection, and moderate reaction in the anterior chamber with no hypopyon formation. A clinical diagnosis of acanthamoeba keratitis was made. Deep corneal scrapings of both corneas were obtained with a sterile surgical blade for cytopathologic examination and culture. The scrapings were placed on glass microscope slides, fixed in 95 % ethanol, and stained with gram stain, Masson stain, and calcofluor. Examination with a light microscope failed to reveal amebas. Confirmation of the clinical diagnosis of acanthamoeba keratitis was attempted by excising a fragment of the contact lens with sterile scissors and mounting it on a glass micro-