Filtering Blebs and Aqueous Pathway: An Immunocytological Study

Abstract

Abstract: : Purpose: Transconjunctival filtration is one of the main aqueous humor pathways in glaucoma filtering surgery and biomicroscopic observation of microcysts at the surface of the filtering blebs is an important clinical indicator of good–working blebs. The aqueous cellular pathway through the bleb however is not fully defined. We analyzed impression cytology (IC) specimens of various types of blebs with immunocytochemistry under a confocal microscope in order to characterize the bleb at the cellular level. In vivo analysis of the blebs was also performed with a new generation in vivo confocal microscope. Methods: 20 glaucoma patients who underwent filtrating surgery were included in the study (ten functional blebs– thin, elevated and responsible for controlled IOP– and ten flat fibrotic blebs). Confocal microscopy (HRT II Cornea module) was performed in vivo at the level of each bleb. Impression cytology specimens were collected from each bleb to evaluate ex vivo, with a confocal microscope the presence of MUC5AC–positive cells using a technique of indirect immunofluorescence. Both evaluations were conducted in a masked manner. Anti–vimentin antibodies were used in order to identify inflammatory cells. Results: In all IC specimens, numerous MUC5AC–positive cells were observed outside the edges of the bleb and at the surface of the non–working blebs. Empty goblet cells well visible morphologically but with low or no MUC5AC immunostaining characterized the surface of the functional blebs. These empty spaces were correlated to the presence of microcysts observed in vivo with the confocal microscope. Occasional inflammatory cells were found with both techniques, scattered throughout the conjunctival epithelium. Conclusions: Microcysts observed at the surface of functional blebs seem to correspond to empty goblet cells mostly containing aqueous humor instead of gel–forming mucins. Goblet cells have a highly hydrophylic content due to the presence of mucins. Although this hypothesis requires further confirmation, the transcellular pathway of the aqueous humor throughout the conjunctival epithelium could therefore logically occur at the level of the conjunctival goblet cells toward the ocular surface.

Keywords: imaging/image analysis: clinical • immunohistochemistry • wound healing