Working Diagnosis:
Acanthamoeba Keratitis

Treatment:
Chlorohexidine 0.02% and Desomedine 0.1% solution alternated every 30 minutes. Then polyhexamethylene biguanide 0.02% and neomycin/polymixin b/gramacidin solutions during waking hours and every 2 hours during sleeping hours.

Outcome:
The patient continued to be increasingly symptomatic with the toxicity and frequency of drops. The symptoms peaked at about 7 days after treatment was started and approximately 4 weeks after initial presentation. Also during this period he had begun to have symptoms in his right eye at which time treatment was started for this eye as well. After 14 days of treatment he began to have improvement of symptoms, and upon re-evaluation he had clinical improvement Case Photo #3 of the dendritic keratitis on day 41. Treatment was tapered over time and the patient regained baseline visual acuity. Throughout the work-up and treatment the patient was able to participate in athletics, except for the 2 weeks of peak symptoms. Visual acuity and symptom severity were used for guidance of return to play. He was protected throughout with a polycarbonate shield.

Author's Comments:
Acanthamoeba keratitis is uncommon with an incidence in contact lens wearers of 1.65-2 per million in the USA. Greater than 85% can be linked to contact lens wearers and association with contaminated water (well, tap, swimming pools, or freshwater). Common presenting symptoms are pain, photophobia, and increased tearing. Recognition and treatment within 3 weeks is essential for a good prognosis. Failure to respond to first line conjunctivitis therapy indicates a need for consideration of acanthamoeba keratitis. Diamidines and biguanides are the most effective cysticidal anti-amoebics in vitro which carry significant side effects. Mean duration of therapy is 4-5 months. Delayed treatment of keratitis can lead to possible blindness. Complications of cataracts and glaucoma have been reported in as many as 21% of patients.

Editor's Comments:
- This case highlights the importance of close follow-up and re-evaluation of the working diagnosis when a patient fails to improve with initial treatment.
- Prompt referral for expert consultation was obtained, and the patient fortunately had a good outcome.

References:
Dart J, Saw V, Kilvington S. Acanthamoeba Keratitis: Diagnosis and Treatment Update 2009. Am J Ophthalmol 2009;148:487-499.

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