[Painless acanthamoeba keratitis]

Acanthamoeba keratitis is a severe, painful corneal infection found in contact lens wearers. The entity can easily be confused with herpetic or fungal keratitis, especially if no ocular pain is reported.

A 32-year old myopic female presented a unilateral keratitis of unknown etiology since 3 weeks. Administration of topical antiviral substances and corticosteroids led only to temporary improvement of the condition. The patient complained of photophobia but not of ocular pain. The affected eye showed corneal edema, central stromal thickening, descemet's striae as well as fibrin deposits on the corneal endothelium and in the anterior chamber.

An aqueous specimen was negative for a viral infection. A culture for bacteria was negative. Staphylococci were cultured from corneal scrapings and Enterococci from the contact lens solution. Another corneal scraping revealed Acanthamoeba class II (6 weeks after the onset of symptoms).

Under treatment with propamidine, polymyxin b, neomycin, gramicidin and polyhexidine (topical) as well as fluconazole/ketoconazole (systemic) the diameter of the annular infiltrate, which had developed decreased, but the infiltrate persisted. In the further course, the infiltrate persisted while the amount of fibrin in the anterior chamber increased. Penetrating keratoplasty was performed. Histologic examination of the host corneal tissue revealed massive infiltration with Acanthamoeba.

Severe pain and history of wearing contact lenses are features suggestive of Acanthamoeba keratitis. The patient presented here had a history of contact lens wear, but no ocular pain was reported. The characteristic annular infiltrate had a late onset. Bacterial superinfection could not be ruled out. Therapeutic penetrating keratoplasty had to be performed as the condition deteriorated inspite of intensive chemotherapy. With penetrating keratoplasty a good visual acuity could be regained.