Acanthoamoeba Keratitis Induced by a Therapeutic, Soft Contact Lens: Diagnosis via Gram Staining

Purpose: We report two cases of Acanthamoeba keratitis diagnosed by Gram staining in patients who had recently worn therapeutic, soft contact lenses and had no history of lens use for visual correction.Case summary: The first patient was initially diagnosed with suspected mixed bacterial or fungal keratitis before a final diagnosis of Acanthamoeba keratitis was confirmed by Gram staining of a corneal smear. The second patient was initially diagnosed with a persistent epithelial defect caused by an earlier lid injury inflicted by a metallic foreign body, and then with a suspected mixed infection combined with herpetic uveitis. The patient was finally diagnosed with Acanthamoeba keratitis by Gram staining of a corneal smear. Both cases were treated with polyhexamethylene biguanide and chlorhexidine.Conclusions: Therapeutic, soft contact lenses are used to enhance corneal, epithelial wound healing in conjunction with antimicrobial prophylaxis. However, application of such a lens to a diseased cornea may predispose to the development of microbial keratitis caused by microorganisms resistant to the usual, prophylactic, antimicrobial eye drops. Therapeutic, soft contact lenses are associated with a risk of Acanthamoeba keratitis; early diagnosis is important. Gram staining of a corneal smear is useful in this context. Acanthamoeba is not eradicated by empirical broad-spectrum antimicrobials.