The histopathology of filamentary keratitis.

Filamentary keratitis is characterized by the presence of fine filaments of epithelium and mucus that are attached to the cornea. The exact pathogenesis of this entity has remained unclear. One reason has been the lack of pathologic specimens of corneas from patients with filamentary keratitis. We examined the corneas of a patient who had died while suffering from filamentary keratitis. Scattered groups of inflammatory cells and fibroblasts were present just below the basal epithelium. It seemed that these cells had disrupted the epithelial basement membrane and Bowman's layer. To our knowledge, this is the first postmortem analysis of a cornea in a patient with acute filamentary keratitis. These findings support the theory that filamentary keratitis results from damage to the basal epithelial cells, epithelial basement membrane, or both.