Conjunctivitis: A Primer on Conjunctival Biopsy and Approach to Histopathologic Diagnosis.

Conjunctivitis, or inflammation of the mucosal covering the anterior third of sclera and inner eyelid, is a common clinical condition of varied causation. Most cases are self-limited due to infection or allergy and rarely necessitate biopsy. Inflammation of the conjunctiva, however, is one of the most common principal histopathologic diagnoses rendered when the tissue is biopsied. In the context of conjunctivitis, biopsy is usually performed when inflammation is chronic and recalcitrant to therapy, has clinically atypical features, or requires an etiologic diagnosis when one cannot be reached through other laboratory methods. The exclusion of ocular surface neoplasia in a chronically inflamed conjunctiva is a common justification for biopsy. When inflammation is the principal histopathology finding, it is desirable-whenever feasible-to establish the cause. This brief review provides a guide in how histologic findings of an inflamed conjunctiva can direct the clinical evaluation towards an etiologic diagnosis.