Complicated Diagnosis and Treatment of Rare Painless Acanthamoeba Keratitis

<b>Objectives</b>: The aim was to present the complicated diagnostic and therapeutic process of atypical, painless keratitis caused by a cosmopolitan protozoan of the genus <i>Acanthamoeba</i>. <b>Methods</b>: This Case Report describes a medical case involving a 48-year-old woman who occasionally wears soft contact lenses and was referred to our hospital for treatment due to deteriorating visual acuity in her left eye. The diagnostic process included the isolation of amoebae from corneal scrapings and the morphological and molecular identification of the etiological agent of the infection. <b>Results</b>: After examination, painless atypical keratitis was diagnosed, initially considered recurrent herpetic keratitis. However, antiviral treatment did not bring about any improvement. Further observation revealed a dense, central, annular infiltrate on the periphery of the cornea. Despite treatment, the corneal infiltrate did not improve and the patient required therapeutic penetrating keratoplasty. Ultimately, the patient underwent combined surgery: corneal transplantation with cataract phacoemulsification and intraocular lens implantation. The postoperative course was uneventful. <b>Conclusions</b>: <i>Acanthamoeba</i> keratitis should be included in the differential diagnosis of keratitis, even in the absence of its characteristic feature of severe ocular pain, especially in contact lens wearers and patients who have had herpetic keratitis. Infection of the cornea with the <i>Herpes simplex</i> type 1 virus causes nerve degeneration, which probably translates into a painless course of <i>Acanthamoeba castellanii</i> infection.