Histopathology of a functioning mitomycin-C trabeculectomy

The ideal trabeculectomy bleb is diffuse, normally vascularized and characterized by microcystic change in the overlying conjunctiva. We compare and contrast the histopathology of a normally functioning mitomycin-C trabeculectomy site obtained from an eye enucleated for iris melanoma with abnormal blebs discussed in the literature. Representative sections of the normally functioning bleb were examined under the light microscope. The conjunctiva is composed of a uniform three-layered non-keratinizing stratified squamous epithelium overlying a single layer of oedematous basal cells. The conjunctival stroma consisted of loose connective tissue, traversed by capillaries and scattered small cystic spaces lined by endothelial cells. There were no goblet cells and few inflammatory cells and fibroblasts. The scleral trapdoor was evident as a cleft in the scleral wall in communication with the anterior chamber at the surgically created sclerostomy. Because the histopathological findings in our case correlate well with this clinical appearance, we conclude that whereas augmentation with anti-metabolites, such as mitomycin-C, can be associated with significantly altered conjunctival histopathology and consequent hypotony, but, if used carefully, normal architecture is conserved.