Acanthamoeba keratits is a sight threatening infection, which most commonly affects contact lens wearers. We present a case of Acanthamoeba polyphaga and Acanthamoeba castellanii in a 59-year old contact lens wearer, managed using oral miltefosine (Impavido; manufacturer Asta Medica).

A 59-year old gentleman, a contact lens wearer, was referred to our tertiary corneal service from a neighbouring hospital. The vision was hand movements in the left eye, and 6/6 in the right eye. Clinical examination revealed perineurial infiltrates, stromal infiltrates and a 1.5mm hypopyon, strongly suggestive of acanthamoeba keratitis. This was confirmed by a corneal scrape. Initial management included topical biguanide and diamidine (polyhexamethylene biguanide (PHMB) 0.02%, later 0.06%, and hexamidine 0.1%). Despite this, a further corneal scrape revealed persistent Acanthamoeba infection. Therefore treatment with imidazole (guttae voriconazole, oral posaconazole) and fortified biguanide (chlorhexadine 0.2%) was commenced. Therapeutic penetrating keratoplasty was performed, microscopy revealed Acanthamoeba throughout the host stroma.

Corneal scrape and AC tap showed persistent infection with Acanthamoeba. Treatment was changed to fortified biguanide (PHMB 0.06%), and intracameral voriconazole was administered twice. Clinical examination revealed scleritis and there were concerns regarding posterior segment involvement. Oral miltefosine was commenced with the aim to reduce any further posterior progression. Enucleation was performed 2 weeks later, due to severe necrotic keratitis with almost complete corneal melt. Histopathological analysis detected A.polyphaga and A.castellanii in vitreous but not retina, choroid or optic nerve suggesting that infection had not progressed posteriorly through the ocular structures and the CNS was not involved.

The use of miltefosine as a component of combination antiparasitic therapy is associated with long-term survival in cases of Acanthamoeba infection of the CNS. Our case highlights its first reported use in the potential prevention of posterior ocular progression and CNS involvement in a case of severe refractory Acanthamoeba keratitis.