Clinicopathologic features of excised mitomycin filtering blebs.

Using light and electron microscopy, we examined two conjunctival filtering blebs that had been treated with mitomycin just prior to trabeculectomy and were later excised due to ocular hypotony. Light microscopy showed attenuated epithelium, loosely arranged subepithelial connective tissue, and scattered acute and chronic inflammatory cells. Electron microscopy also showed these findings and demonstrated the presence of presumably viable activated fibrocytes in the subepithelial connective tissue. The presence of inflammatory cells in the blebs was attributed to concurrent infections and suggests that mitomycin does not completely suppress, but may attenuate, the inflammatory response. The mechanism of hypotony and bleb failure in the two eyes was most likely a combination of over-filtration and a persistent wound leak due to a lack of postoperative subconjunctival fibrosis secondary to treatment with mitomycin.