Histopathologic features of conjunctival filtering blebs

Objectives: To characterize and compare the histological features of conjunctiva obtained during the repair of trabeculectomy and inadvertent blebs and to assess the effects of antifibrotic agents. Methods: We used routine paraffin processing and light microscopy to examine conjunctival specimens from 28 eyes undergoing late bleb revision: 19 leaking trabeculectomy blebs, 5 nonleaking trabeculectomy blebs, and 4 inadvertent blebs. Quantitative analysis of histological characteristics included conjunctival epithelial thickness, stromal vascularity, squamous metaplasia, stromal inflammatory cell infiltrate, and goblet cell density. The type of surgery, presence of leaks, prior topical medication, and antifibrotic use were correlated with histological findings. Results: Trabeculectomy blebs (leaking and nonleaking) showed decreases in overall epithelial thickness (P < .02), goblet cell density (P < .001), and vascularity (P < .001) compared with inadvertent bleb controls. Conjunctiva exposed to antifibrotics had fewer layers of epithelial cells than those with no prior exposure (P < .05). Conclusions: Histological analysis of thin blebs excised following trabeculectomy demonstrated decreases in epithelial thickness and goblet cell density compared with inadvertent blebs. Both leaking and nonleaking trabeculectomy blebs exhibited decreases in localized stromal vascularity and increases in surrounding stromal vascularity compared with normal conjunctiva.