Acanthamoeba Keratitis After Laser-Assisted In Situ Keratomileusis (LASIK) Successfully Treated With Polyhexamethylene Biguanide (PHMB) 0.08% Monotherapy: A Case Report

A man in his early 30s presented with progressive unilateral ocular pain and visual deterioration three months after uncomplicated bilateral laser-assisted in situ keratomileusis (LASIK). Initial treatment for presumed bacterial keratitis, followed by herpes simplex keratitis, failed to result in improvement. He was referred to our corneal service, where in vivo confocal microscopy demonstrated characteristic Acanthamoeba cysts within the corneal stroma. The patient was commenced on polyhexamethylene biguanide (PHMB) 0.08% monotherapy through an Early Access Programme in accordance with the Orphan Drug for Acanthamoeba Keratitis protocol, with subsequent clinical and symptomatic improvement. Resolution was achieved without the use of topical corticosteroids. This case highlights the diagnostic difficulty of Acanthamoeba keratitis in post-refractive surgery patients without a history of contact lens use and emphasises the importance of early clinical suspicion, advanced diagnostics, and protocol-based therapy to optimise outcomes.