Pathological characteristics of the different stages of Acanthamoeba keratitis.

AIMS: To classify the clinical stages of Acanthamoeba keratitis (AK), and clarify the relationship between pathological changes and clinical features.

METHODS AND RESULTS: Between January 2007 and May 2012, AK was diagnosed in 11 eyes by pathological examination and confocal laser scanning microscopy. Pathological investigation of all cornea samples from keratoplasty was done with periodic acid-Schiff and haematoxylin and eosin stains. AK clinical stage, pathological features and postoperative treatment were studied retrospectively. The 11 cases were classified into development stage, convalescence stage, or cicatricial stage. In the development stage, marked conjunctival hyperaemia, a corneal epithelial defect, obvious corneal infiltration and progressive inflammation were seen; pathological changes comprised abundant inflammatory cells and a rounded cyst in the oedematous stroma, as well as a very small amount of neovascularization. In the convalescence cases, moderate conjunctival hyperaemia, corneal disciform structures, repair of the corneal epithelial defect and abundant neovascularization were seen; pathological changes included significant tissue necrosis and a small, shrunken cyst in the stroma, as well as significant neovascularization. In the cicatricial stage, keratoleukoma was seen; pathological changes comprised a few inflammatory cells and shrunken cysts scattered in the stroma. There were no cases of recurrence.

CONCLUSIONS: The pathological features of different clinical stages confirmed the new clinical classification of AK.