Acanthamoeba keratitis (AK) is an infectious disease of the ocular surface that can be challenging to diagnose and treat and can lead to permanent loss of vision. It is most common in contact lens wearers, with reported rates of 1 to 33 cases per million contact lens wearers. 1,2 Acanthamoebae are protozoans ranging 25 to 50 um in size that can exist in either an active trophozoite or dormant cyst form. Several species of Acanthamoeba have been reported to cause AK, including A. castellanii and A. polyphaga. The cyst form can survive low temperatures and is resistant to biocides, chlorination, and antibiotics. 3 Patients can present with a variety of symptoms and signs that may be initially misdiagnosed as bacterial or viral keratitis. AK should be included in the differential diagnosis of any case presenting with unilateral keratitis, especially in the setting of contact lens wear, trauma, or contamination with soil or water. Patients typically present with pain, photophobia, and decreased visual acuity (VA). 4 Early findings include epitheliitis, with punctate keratopathy and pseudodendrites, often leading to a presumptive diagnosis of Herpes simplex keratitis. Patients may progress and develop perineural infiltrates, anterior stromal disease, deep stromal keratitis, or a ring infiltrate. 5 Although a ring infiltrate and perineural infiltrates are conventionally thought to be pathognomic for AK, they only occur in about 50% and 63% of cases, respectively, 4,6 and are findings that develop later in the disease course. Since the likelihood of medical cure is greater if diagnosis is made while the infection remains superficial, prompt recognition of the disease before the development of these later pathognomic signs is important. 5 Clinicians must consider risk factors, clinical course, and response to therapy in arriving at a preliminary