Amoebic keratitis

Amoebic keratitis, also known as Acanthamoeba keratitis (AK), is a rare but serious infection of the cornea (the clear front surface of the eye) caused by free-living amoebae of the genus Acanthamoeba. These microscopic organisms are ubiquitous in the environment, found in soil, freshwater, and even tap water. The infection predominantly affects the eye, specifically the corneal epithelium and stroma, and can lead to severe pain, photophobia (sensitivity to light), excessive tearing, blurred vision, and a characteristic ring-shaped corneal infiltrate. The condition is strongly associated with contact lens wear, particularly when lenses are exposed to contaminated water or improperly cleaned. Other risk factors include corneal trauma and exposure to contaminated water sources. The disease can be difficult to diagnose early because its symptoms often mimic those of other forms of infectious keratitis, such as herpes simplex keratitis or bacterial keratitis. Delayed diagnosis frequently leads to worse outcomes. Diagnosis is typically confirmed through corneal scraping with culture on non-nutrient agar seeded with bacteria, confocal microscopy, or polymerase chain reaction (PCR) testing. If left untreated or inadequately treated, Acanthamoeba keratitis can progress to corneal ulceration, perforation, and potentially permanent vision loss. Treatment is prolonged and challenging, typically involving a combination of topical antiseptic agents such as polyhexamethylene biguanide (PHMB) or chlorhexidine, often combined with a diamidine such as propamidine isethionate (Brolene). Treatment courses frequently last several months due to the organism's ability to form resistant cysts. In severe or refractory cases, corneal transplantation (penetrating keratoplasty) may be necessary. Early diagnosis and prompt initiation of appropriate antimicrobial therapy are critical for preserving vision. Prevention strategies focus on proper contact lens hygiene and avoiding exposure of lenses to water.

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