title: Decreased corneal sensation as an initial feature of Acanthamoeba keratitis.
abstract: BACKGROUND
  Herpes simplex keratitis is the most common misdiagnosis in patients with Acanthamoeba keratitis, which is increasing in frequency and is associated with daily wear soft contact lenses. Both entities usually present as unilateral keratitis. The manifestations of superficial Acanthamoeba keratitis (i.e., unilaterality, dendriform appearance, positive response to antivirals, and decreased corneal sensation) increase the opportunity for misdiagnosis as herpes simplex keratitis. The authors have encountered six patients with Acanthamoeba keratitis in whom the correct diagnosis was delayed from 2 weeks to 3 months.
  
  
  METHODS
  All six patients underwent testing with the Cochet-Bonnet esthesiometer and extensive pharmacologic treatment for herpes simplex keratitis. Corneal scrapings were taken between 2 and 6 weeks after the initial examination.
  
  
  RESULTS
  In all six patients, corneal sensation was decreased significantly. Drug therapy was ineffective. Cultures were positive for Acanthamoeba. Five of six patients underwent penetrating keratoplasty.
  
  
  CONCLUSIONS
  Decreased corneal sensation has contributed to the misdiagnosis of Acanthamoeba as herpes simplex keratitis. Misdiagnosis results in delayed treatment and worse outcome. The authors found that significantly decreased corneal sensation is a frequent finding in early Acanthamoeba keratitis. Therefore, physicians should consider Acanthamoeba keratitis as an alternative diagnosis in patients with presumed herpes simplex keratitis with decreased corneal sensation.
authors.affiliation: Department of Ophthalmology, North Shore University Hospital, Manhasset, New York 11030, USA.
authors.forename: H D
authors.initials: HD
authors.lastname: Perry
authors.forename: E D
authors.initials: ED
authors.lastname: Donnenfeld
authors.forename: G N
authors.initials: GN
authors.lastname: Foulks
authors.forename: K
authors.initials: K
authors.lastname: Moadel
authors.forename: A J
authors.initials: AJ
authors.lastname: Kanellopoulos
mesh_terms: D000048:Acanthamoeba / Q000302:isolation & purification; D015823:Acanthamoeba Keratitis / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery; D000328:Adult; D000818:Animals; D003261:Contact Lenses / Q000009:adverse effects; D003315:Cornea / Q000469:parasitology / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D016849:Keratitis, Herpetic / Q000175:diagnosis; D015948:Keratoplasty, Penetrating; D008297:Male; D012678:Sensation Disorders / Q000175:diagnosis* / Q000469:parasitology