Retrospective Study of Acanthamoebic Keratitis During the Past 10 Years

Overview

Acanthamoebic keratitis is an important corneal disease which may cause severe complication. The difficulty in diagnosis, the difficulty in treatment, and the long treatment process are factors leading to the poor prognosis of these patients. In this retrospective study, the investigators try to analyze the tissue proven Acanthamoebic keratitis diagnosed in our hospital. The investigators will focus on the in vivo confocal microscopic results, the medical history and the medical/surgical treatment outcome. The investigators will collect the tissue proven cases according to the data provided by laboratory diagnosis department and pathological department. The in vivo confocal microscopic results will be collected and analyzed. The investigators will also look through the photography of the external eyes from data stored in PAC system. The medical history and treatment outcome will be studied from clinical chart review. From this study, the investigators aimed to find out a easy way of diagnosing Acanthamoebic keratitis from in vivo confocal microscopy, and find out a better way for treatment.

Acanthamoeba keratitis (AK), caused by a pathogenic amoeba, is a sight-threatening corneal infection with severe pain, epithelial defect, epithelial haze, pseudodendrites, and, most characteristically, radial keratoneuritis. The corneal infection of AK was first recognized in the mid 1970s. Since then, a growing number of AK cases were diagnosed, mainly resulting from improper use of soft contact lenses. Clinical diagnosis of AL is difficult, especially in the early phases of the disease, and it often is misdiagnosed and treated as a herpes simplex infection. It was reported a diagnostic delay of more than 18 days between onset of symptoms and start of anti- amoebic treatment results in a poor disease progress. While definitive diagnosis is made by confirmation of Acanthamoeba cysts or trophozoites in corneal lesions by staining, corneal biopsy, or tissue culturing. In vivo confocal microscopy was considered useful in the rapid diagnosis of AK. The Acanthamoeba cysts were observed almost exclusively in the epithelial cell layer as highly reflective, round or stellate, high-contrast particles with a diameter of 10 to 20 μm. It was suggested that invasion of Acanthamoeba cysts into Bowman's layer may be a useful predictor for a persistent clinical course. The trophozoites are pear-shaped or irregularly wedge-shaped structures, some surrounded by a brilliant halo some exhibiting fine pseudopodia-like extensions, with mean size of 30.2 µm (range 19.2-55.6μm). It was reported to present in cornea stroma. Highly reflective activated keratocytes forming a honeycomb pattern change was reported to be present around the keratoneuritis. In addition, infiltration of inflammatory cells, possibly polymorphonuclear cells, was observed along with the keratocytes in cases of AK. However, the in vivo confocal microscopic findings in patients with AK is still limited. Some clinical findings may not be correlated with the reports published before. John K.G. et al recommended clinical treatment toward Acanthamoeba keratitis using Diamidine and Biguanide which are the only two proofed Acanthamoeba cysticidal medication, while Metronidazole is effective in vivo but not in vitro. Topical steroid was considered rather controversial but important and beneficial. It was recommended to use a minimum of 2 weeks of Biguanide prior to the use of topical steroid for inflammation control. When Acanthamoeba keratitis was diagnosed early in the disease course, topical steroid can be spared for the immediate using Diamidine and Biguanide to kill pathogen. In a United Kingdom multicenter study of 218 patients, the average duration of medical therapy was 6 months (range, 0.5 to 29 months). In 2011, a little over half of respondents using corticosteroids in the treatment of Acanthamoeba keratitis. Surgical managements including epithelial debridement, cryotherapy and corneal graft surgery may itself be therapeutic if performed early and promote penetration. Therefore, when Acanthamoeba keratitis was suspected, a long-term and immediate medical treatment may be needed ,and the use of topical steroid toward Acanthamoeba keratitis is still worth investigating.