Acanthamoeba Keratitis

Acanthamoeba keratitis (AK) is a newly recognized infectious keratitis (1973), rising yearly. Complex diagnosis/treatment; often misdiagnosed as HSV/fungal keratitis.

Common Symptoms

Eye pain; keratitis; abscess; corneal ulcer

Causes and Pathogenesis

(1) Etiology: free-living pathogenic amoebae ubiquitous in fresh/salt water/soil/dust/debris/rotting plants/fece; isolated from bathtubs/air filters/cooling towers/contact lens/solutions. (a) Acanthamoeba: fecally contaminated soil/water; trophozoite (15-45 µm, acanthopodia) and cyst (10-25 µm, double wall, ostiole). Cyst resistant to antibiotics/chlorine/disinfectants, survives years in environment. 25 species; 8 pathogenic to humans (A. castellanii/culbertsoni/hatchetti/lugdunensis/polyphaga/quina/rhysodes/griffini). (b) Naegleria: fresh water; 7×20 µm amoeboid; flagellated form; cyst 9 µm. (c) Classification: morphology (Pussard/Pons 1977: 18 species, 3 groups; pathogenic mainly group II); genotyping (18S rDNA; Beijing 2004: 25/26 = T4, 1 = T3). (2) Pathogenesis: contact/opportunistic; lipopolysaccharide binding to corneal epithelium; neuraminidase/enzymes → epithelial thinning/necrosis → stromal invasion. Three injury mechanisms: (i) phagocytosis of membrane; (ii) spontaneous secretory lysosomal enzymes; (iii) membrane-triggered enzyme release.

Treatment

Drug, supportive, surgical therapy

Preventive Measures

Contact lens hygiene education; never sleep in lenses; never use tap water/home-made saline.

Department to Visit

It is recommended to visit the Ophthalmology department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.