A 41-year-old woman presented to the ophthalmology clinic with a 2-month history of intermittent pain, blurry vision, and sensitivity to light in her left eye. She wore monthly disposable soft contact lenses that she kept in her eyes while swimming and showering. The patient had difficulty keeping her left eye open during the physical examination, which revealed redness of the conjunctiva. The visual acuity was 20/20 in the right eye and 20/200 in the left eye. A large, ring-shaped infiltrate was present in the left eye, along with corneal haze and an overlying epithelial defect, which showed uptake of fluorescein dye. Cultures from corneal scrapings grew Acanthamoeba polyphaga. She received a diagnosis of acanthamoeba keratitis, a vision-threatening infection most commonly associated with contact lens wear. The patient was treated with topical polihexanide and propamidine isethionate. Although the infection resolved, the vision in her left eye was not restored, owing to a dense, central corneal scar and cataract. Twelve months after the initial presentation, the patient underwent deep anterior lamellar keratoplasty, which resulted in a postoperative visual acuity of 20/80 and no discomfort in her left eye.