Case series: Delayed diagnoses of Acanthamoeba keratitis

PURPOSE: To describe two cases of Acanthamoeba keratitis in contact lens wearers misdiagnosed as Herpes simplex keratitis. OBSERVATIONS: Case 1 is a 54-year-old male that was misdiagnosed with Herpes simplex keratitis who developed advanced Acanthamoeba keratitis. His treatment course was complex and involved both medical therapy and surgical intervention with poor resolution. Case 2 is an 18-year-old male who was also initially misdiagnosed and treated for Herpes simplex keratitis, but ultimately treated with polyhexamethylene biguanide and chlorhexidine with complete resolution. CONCLUSIONS AND IMPORTANCE: The clinical presentation of Acanthamoeba keratitis may closely resemble other causes of keratitis and continues to be misdiagnosed, leading to delayed diagnosis and treatment. However, given the significant morbidity and challenging treatment course for Acanthamoeba keratitis, it is important for clinicians to maintain a high suspicion for Acanthamoeba and to consider obtaining cultures in contact lens wearers with atypical keratitis prior to making a diagnosis of Herpes simplex keratitis.