In vivo confocal microscopy study of blebs after filtering surgery

Objective: To analyze bleb structure after filtering surgery at the cellular level using a new generation in vivo confocal microscope. Design: Observational case series. Participants: We retrospectively evaluated 17 filtering blebs of 13 patients after trabeculectomy. Methods: Ophthalmologic examinations included slit-lamp examination, applanation tonometry, and in vivo confocal microscopy (Heidelberg Retina Tomograph II, Rostock Cornea Module). Eyes were classified into 3 groups: (1) functioning blebs (6 eyes), (2) nonfunctioning blebs (6 eyes), and (3) functioning blebs after application of mitomycin C (5 eyes). Cellular patterns, morphologic appearance, and functional aspects of functioning and nonfunctioning blebs were compared in a masked manner. Main Outcome Measures: In vivo confocal microscopy images were analyzed for number of intraepithelial microcysts, density of subepithelial connective tissue, presence of blood vessels, or encapsulation. Results: All functioning blebs had numerous intraepithelial optically-empty microcysts, whereas all nonfunctioning blebs had none or few. Subepithelial connective tissue was widely spaced in all functioning blebs, whereas the tissue was dense in 83.3% of nonfunctioning blebs. Functioning blebs with mitomycin C had numerous microcysts and loosely arranged subepithelial connective tissue as compared with nonfunctioning blebs. Conclusions: In vivo confocal microscopy study of blebs is an original method that agrees well with ex vivo histologic examination. The number of microcysts and the density of the subepithelial connective tissue observed with in vivo confocal microscopy are correlated with bleb function. By providing details of the structures of filtering blebs at the cellular level, in vivo confocal microscopy constitutes a new promising way to understand wound healing mechanisms after filtering surgery.