Culture Negative Confoscan Positive Acanthamoeba Keratitis: A relentless course.

Department of Ophthalmology, Sultan Qaboos University Hospital, Muscat, Sultanate of Oman.
Sultan Qaboos University medical journal 12/2009; 9(3):338-40.
Source: PubMed

ABSTRACT Acanthamoeba keratitis is a protozoal infection of the eye, mainly due to the use of non-sterile solutions, like saline for disinfecting contact lenses. We report a case where delay in the diagnosis of acanthamoeba keratitis due to inadequate laboratory investigations and clinical management led to an excruciatingly painful course of the disease. The importance of non-invasive imaging techniques of confocal microscopy in the diagnosis of acanthamoeba keratitis, in the absence of positive culture reports, is highlighted in this case.

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    ABSTRACT: Tandem scanning confocal microscopy was performed on two patients with Acanthamoeba keratitis to provide images detailing characteristic findings of the disease. Although tandem scanning confocal microscopy of Acanthamoeba has been described in previous reports, Acanthamoeba keratitis has not been fully characterized with this instrument. In vivo confocal micrographs showed the double-walled structure of the Acanthamoeba cyst and associated radial keratoneuritis (perineuritis). We reviewed the records of two patients with a clinical diagnosis of Acanthamoeba keratitis, one with culture-proven Acanthamoeba and the other with a suspected Acanthamoeba infection. Slit-lamp biomicroscopy and in vivo tandem scanning confocal microscopy were performed. The images obtained were compared with images from patients without corneal disease. High-contrast round bodies suggestive of Acanthamoeba cysts, as previously described, and irregular forms suggestive of Acanthamoeba trophozoites were found by tandem scanning confocal microscopy. Additionally, we showed conclusively that under certain circumstances (that is, corneal scarring) tandem scanning confocal microscopy can resolve the double-walled structure of the Acanthamoeba ectocyst surrounding the endocyst. Furthermore, radial keratoneuritis was demonstrated, consisting of an irregularly swollen nerve fiber with probable amoebic infiltration. Confocal microscopy can be a useful, noninvasive imaging technique helpful in the study, diagnosis, and treatment of Acanthamoeba keratitis.
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    ABSTRACT: Three myopic patients who wore soft contact lenses developed unilateral Acanthamoeba keratitis that presented with unusual infiltrates that appeared to be located along the corneal nerves. These infiltrates were found in the midstroma, beginning paracentrally, and extending to the limbus in a radial pattern. The epithelium overlying these infiltrates was intact. In two patients, the central epithelium had a stippled, almost dendritiform appearance leading to the misdiagnosis of herpes simplex keratitis. Cultures from corneal scrapings of two patients and cultures of a corneal biopsy from one patient, which included an area of presumed neural involvement, grew Acanthamoebae. All three patients used homemade saline solutions (salt tablets dissolved in distilled water). In one patient, Acanthamoebae were found in the contact lens case solution. In our recent experience, Acanthamoebae have also been found in the distilled water bottle and the saline solution made from distilled water and salt tablets in two additional patients with A. keratitis. Distilled water, which is not sterile, has proven to be one potentially avoidable source of A. keratitis in contact lens wearers.
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    ABSTRACT: The treatment of Acanthamoeba keratitis has been increasingly successful as diagnoses are made earlier. The authors investigated features of the disease and prognosis in a consecutive series of 15 patients who were treated within 1 month of initial symptoms. A database of patients with Acanthamoeba infection presenting between March 1984 and March 1992 was analyzed. The recognition, presenting features, culture methods, results, and treatment of the early cases were reviewed to determine the reasons for a good outcome. Recognition depended on perineural infiltrates (11/15), uveitis (10/15), limbitis (14/15), and infiltrated epithelium; 6 of 15 patients had epithelial defects, but only 3 of 15 had ring infiltrates or ulcers. Epithelial biopsy was culture-positive in 12 of 15 patients. Most (11/15) patients needed only two anti-amebal drugs. One patient only required penetrating keratoplasty for uncontrolled disease. The final visual acuity was at least 6/12 in all patients who had been treated within 1 month of first symptoms, whereas only 17 (53%) of 32 eyes of patients who presented after 1 month achieved a visual acuity of 6/12. Subtle diagnostic signs, supported by comprehensive microbiologic investigation, justify the immediate instigation of specific antiamebal therapy. Treatment within 1 month of onset results in a lower morbidity and a good visual outcome.
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