Corneal biopsy in chronic keratitis.

Failure to identify the causative agent makes the treatment of chronic keratitis difficult. Inability to obtain a definitive diagnosis may be related to the depth of the pathogen within the cornea, partial or inappropriate treatment that interferes with diagnostic cultures, or fastidious growth characteristics of the organism in culture. Biopsy by lamellar keratectomy provides sufficient tissue for culture and for histopathologic evaluation by histochemistry, immunohistopathology, and, if necessary, electron microscopy. Consultation with an ophthalmic pathologist before biopsy can prevent inappropriate handling of the specimen, which may preclude essential diagnostic procedures. Many studies can be done within 24 hours of biopsy, often permitting rapid identification of the pathogen and prompt institution of appropriate therapy.