Corneal Biopsy

Although rarely performed, corneal biopsy may be useful in establishing the diagnosis and prompt institution of appropriate management in progressive keratitis of unknown cause. Inability to obtain a definitive diagnosis in a case of chronic keratitis may be related to previous use of antimicrobials that interfere with standard cultures or by the fastidious growth of unusual pathogens in culture. Surgical techniques employed for corneal biopsy, as well as proper processing of corneal specimens for microbiologic or histopathologic studies, will be reviewed. Indications and concerns about the procedure will also be addressed. HISTORICAL PERSPECTIVE Reports on corneal biopsy started to appear more frequently in the ophthalmic literature during the 1980s. The technique became an exciting adjunct to the clinician’s diagnostic armamentarium as atypical forms of infectious keratitis unresponsive to available antimicrobial therapy were appearing more frequently. This may be explained by the increased popularity of soft contact lenses in the early 1980s. Better comfort and more affordable lenses brought freedom from glasses to millions of people, coinciding with an increased incidence of chronic keratitis caused by parasitic infections. Although corneal scrapings may sometimes reveal acanthamoebal cysts, especially early in the disease process when the pathogen is located more superficially, corneal biopsy has proved to be more dependable in providing a more definitive diagnosis in chronic cases of parasitic keratitis. In fungal keratitis, examination of specimens obtained by corneal biopsy were also found to be superior in quality and yield than corneal scrapings. In addition, scrapings failed to find a causative pathogen in 19% to 27% of cases of bacterial keratitis. However, the need for corneal biopsies has waned in the last decade. Newer and more potent antibiotics for bacterial keratitis, as well as keen awareness of unusual microorganisms and institution of immediate and appropriate cultures and therapy in cases of fungal, parasitic, and mycobacterial infections, has made the need for corneal biopsy less necessary.