Corneal biopsy in the management of progressive microbial keratitis

PURPOSE: To study the indications and role of diagnostic corneal biopsy in the management of patients with progressive microbial keratitis. METHODS: The records of 33 consecutive patients who underwent a diagnostic corneal biopsy from January 1, 1986, to December 31, 1998, were reviewed. The indication for corneal biopsy was progressive infectious keratitis despite intensive broad-spectrum topical antimicrobial therapy, or progressive stromal infiltration inaccessible to corneal scrapings. Microbiologic evaluation of all corneal biopsies was performed, and 11 of the 33 biopsies were also examined histopathologically. RESULTS: A microorganism was isolated from 27 (82%) of the 33 corneal biopsies. Of the six patients with a negative biopsy, a penetrating keraroplasty was per formed in five patients and the pathogen was identified by examination of the corneal button. In one patient no microorganism was identified; however, the infection resolved with topical antimicrobial therapy. The most common risk factor for keratitis was foreign body exposure or corneal abrasion (14 patients). A solid stromal infiltrate was the most common pattern of corneal involvement Corneal biopsy revealed previously unidentified microorganisms that led to a change in antimicrobial therapy in 24, (89%) of the 27 patients and confirmed prior culture results in the remaining 3 patients. Microbiologic evaluation of the corneal biopsy was more sensitive than histopathologic examination. Acanthamoeba was the most commonly isolated pathogen (five cases), followed by Propionibacterium acnes and Fusarium (four cases each). Gram positive organisms were isolated in 16 patients, Only five of the 27 patients with a positive corneal biopsy required a penetrating keratoplasty, in contrast to five of the six patients with a negative corneal biopsy (P = .005). During the 13-year period of the study, only three corneal biopsies were performed in the last 6 years, CONCLUSIONS: Microbiologic evaluation of a diagnostic corneal biopsy contributed significantly to the diagnosis, treatment, and outcome of patients with progressive infectious keratitis. (C) 2000 by Elsevier Science Inc. All rights reserved.