Purpose: To present two cases of minimal pain Acanthamoeba keratitis to alert clinicians to remember Acanthamoeba when evaluating atypical cases of keratitis.
Methods: The histories of two cases were reviewed with attention to clinical presentation subjective complaints, treatment, and long-term outcome.
Results: In case 1, a 24-year-old man presented with decreased vision and an irritated feeling in his eye. He did not wear contact lenses. His initial diagnosis was adenoviral conjunctivitis. One month later, he was diagnosed with atypical herpes simplex keratitis and started on acyclovir. Two weeks later, he was referred to the Cornea Service. Further history revealed the patient to be a professional triathlete who trained by swimming in a fresh water pond. He was found to have an unusually high pain tolerance. Biopsy revealed Acanthamoeba. He was admitted for intensive therapy with neomycin, propamidine isethionate, and polyhexamethylene biguanide. Two years after diagnosis, he has best-corrected visual acuity of 20/100. In case 2, a 28-year-old man with known herpes simplex keratitis presented with decreased vision. He was started on topical trifluridine. After 6 weeks without improvement, he was referred for corneal evaluation. His eye always remained comfortable. Corneal sensation was markedly decreased. Further history revealed that he swam in fresh water. Biopsy was positive for Acanthamoeba. After 1 year of therapy with polyhexamethylene biguanide and neomycin, visual acuity was 20/200, and the patient underwent a corneal transplant.
Conclusion: Acanthamoeba keratitis must be considered in the differential diagnosis of keratitis, even without the classic presentation of severe pain and predisposing corneal trauma, including contact lens wear.