Acanthamoeba Keratitis

Excerpt

Acanthamoeba is a genus of protozoans widely present in various habitats, including water, air, soil, and dust. Initially identified in 1974, Acanthamoeba keratitis (AK) is a sight-threatening ocular infection with a potentially poor prognosis, primarily due to significant delays in diagnosis. The etiology of AK seems multifactorial, with most cases being associated with the use of contact lenses and their cleaning solutions.

In the past 2 decades, there has been a continuous increase in contact lens users coupled with inadequate hygienic practices, elevated risk factors, and improper handling methods, which have led to increased risk of microbial keratitis, especially bacterial keratitis and AK. AK, a painful, sight-threatening condition, profoundly impacts a patient's quality of life.

AK closely mimics other keratitis, often leading to misdiagnosis and delayed treatment. The condition can manifest with a fluctuating course, and nonresolving cases may require therapeutic keratoplasty to preserve vision. AK is a rare corneal pathology with a prevalence of 1 to 9 cases per 100,000 individuals. The incidence of this condition in the Western world is increasing due to its direct association with contact lens usage, which remains the primary risk factor for this condition.

Up to 93% of cases of AK are reported among contact lens wearers, emphasizing the crucial link between this eye infection and contact lens usage. Several risk factors contribute to the occurrence of AK, including inadequate contact lens hygiene, overnight wear, prolonged use, lens use during activities like swimming and showering, exposure to contaminated water, trauma, and the use of contaminated contact lens solution. Disposable contact lens users face an elevated risk, and orthokeratology has also been identified as a contributing factor, with an annual incidence of 7.7 cases per 10,000 individuals.

Acanthamoeba, a free-living protozoan, is omnipresent in freshwater and soil, existing in 2 distinct forms: the dormant cystic form and the motile trophozoite form. The cystic form, characterized by reduced metabolic activity, exhibits resistance against extreme conditions such as temperature variations, dry weather, pH fluctuations, and antiamoebic drugs. Despite advancements in diagnostic and treatment methods, cases of AK are still frequently missed or delayed, leading to detrimental effects on patient outcomes and quality of life. Delayed diagnosis can result in deeper corneal involvement, necessitating urgent keratoplasty to restore ocular anatomy and vision.