Acanthamoeba Keratitis, Pathology, Diagnosis and Treatment

Abstract

Acanthamoeba keratitis is an unusual corneal infection that is recently increasing in frequency and is often contracted by contact lens wearers, someone who experienced recent eye trauma, or someone exposed to contaminated waters. Acanthamoeba survive in air, soil, dust, and water. Therefore, eye trauma and poor contact lens hygiene practices lead to the entrapment of debris and thus infection. Acanthamoeba keratitis results in severe eye pain, inflammation, and defects of the epithelium and stroma that can potentially result in vision loss if not diagnosed early and treated promptly. The disease can be diagnosed using corneal scrape/biopsy, polymerase chain reactions, impression cytology, or in vivo confocal microscopy. Once diagnosed, it is usually treated with an antimicrobial combination therapy of biguanide and aromatic diadine eye drops for several months. Advanced stages of the disease result in vision loss and the need for corneal transplants. Avoiding the risk factors and diagnosing the disease early are the most effective ways to combat Acanthamoeba keratitis.

Keywords: Acanthamoeba; diagnosis; keratitis; pathogenesis; therapy.

Figure 1

A 40-year-old male contact lens user developed severe ocular irritations after using home-made saline solution for cleansing contact lenses. (A) Slit lamp photo showed diffuse, coarse superficial punctate epithelial erosions and mild anterior stromal haze without epithelial defect or stromal infiltrates. (B) Slit lamp photo with retro-illumination of the same cornea readily showed the coarse epithelial erosions and relatively clear stroma. (C) Impression cytology of the central cornea from the same eye showed multiple double-walled Acanthamoeba cysts (triangles) and occasional trophozoites (arrows) scattered among the epithelial cells in the superficial corneal epithelial sheet.

Figure 2

A dense ring corneal infiltrate in a 74-year-old female with a history of extended soft contact lens and intense painful ring corneal ulcer refractory to conventional antibiotic therapy for presumed bacterial corneal ulcer. Her initial corneal culture was negative for microorganisms. Subsequent corneal biopsy revealed multiple Acanthamoeba cysts in corneal stroma.