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

Abstract

Purpose: We report two cases of <i>Acanthamoeba</i> 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 <i>Acanthamoeba</i> 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 <i>Acanthamoeba</i> 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 <i>Acanthamoeba</i> keratitis; early diagnosis is important. Gram staining of a corneal smear is useful in this context. <i>Acanthamoeba</i> is not eradicated by empirical broad-spectrum antimicrobials.