Acanthamoeba keratitis: diagnosis and treatment update 2009

Am J Ophthalmol. 2009 Oct;148(4):487-499.e2. doi: 10.1016/j.ajo.2009.06.009. Epub 2009 Aug 5.


Purpose: To describe the current management of Acanthamoeba keratitis (AK).

Design: A perspective based on the literature and author experience.

Results: Early diagnosis and appropriate therapy are key to a good prognosis. A provisional diagnosis of AK can be made using the clinical features and confocal microscopy, although a definitive diagnosis requires culture, histology, or identification of Acanthamoeba deoxyribonucleic acid by polymerase chain reaction. Routine use of tissue diagnosis is recommended, particularly for patients unresponsive to treatment for AK. Topical biguanides are the only effective therapy for the resistant encysted form of the organism in vitro, if not always in vivo. None of the other drugs that have been used meet the requirements of consistent cysticidal activity and may have no therapeutic role. The use of topical steroids is controversial, but probably beneficial, for the management of severe corneal inflammatory complications that have not responded to topical biguanides alone. The scleritis associated with AK is rarely associated with extracorneal invasion and usually responds to systemic anti-inflammatory treatment combined with topical biguanides. Therapeutic keratoplasty retains a role for therapy of some severe complications of AK but not for initial treatment. With modern management, 90% of patients can expect to retain visual acuity of 6/12 or better and fewer than 2% become blind, although treatment may take 6 months or more.

Conclusions: Better understanding of the pathogenesis of the extracorneal complications, the availability of polymerase chain reaction for tissue diagnosis, and effective licensed topical anti-amoebics would substantially benefit patients with AK.

Publication types

  • Review

MeSH terms

  • Acanthamoeba / pathogenicity
  • Acanthamoeba Keratitis / diagnosis*
  • Acanthamoeba Keratitis / etiology
  • Acanthamoeba Keratitis / therapy*
  • Animals
  • Biguanides / adverse effects
  • Biguanides / therapeutic use
  • Contact Lenses / parasitology
  • Cryotherapy
  • Early Diagnosis
  • Glucocorticoids / adverse effects
  • Glucocorticoids / therapeutic use
  • Humans
  • Keratoplasty, Penetrating
  • Microscopy, Confocal
  • Prognosis
  • Risk Factors


  • Biguanides
  • Glucocorticoids