Correlation between morphologic appearance and function of filtering bleb in vivo.

Abstract

Efficacy and long-term success of trabeculectomy largely depends on the postoperative development of a functioning filtering bleb. This study was designed to observe histological changes in filtering blebs after trabeculectomy using in vivo confocal microscopy (IVCM), and to investigate the correlation between morphologic appearance and function of filtering blebs. A total of 46 glaucoma patients who had received a trabeculectomy unilaterally in the past 1 to 60 months underwent slit-lamp examination, applanation tonometry, and in vivo confocal microscopy. Eyes were classified into 4 groups according to the morphologic appearance of the filtering bleb based on the Kronfled system: type I blebs (8 eyes), type II blebs (14 eyes), type III blebs (16 eyes), and type IV blebs (8 eyes). The IVCM images were analyzed for the number of intraepithelial microcysts, the density of subepithelial connective tissue and the presence of blood vessels. Type II blebs presented with numerous intraepithelial vacuolar microcysts, while several large intraepithelial microcysts were found in type I blebs. Subepithelial connective tissue was widely spaced in type I and II blebs. In contrast, type III and IV blebs showed few or no intraepithelial microcysts, and subepithelial connective tissue was densely distributed. Neovascularization was seen in 83.3% of failed blebs, whereas neovascularization was found in only 16.6% of successful blebs. Different types of blebs reveal various histological characteristics at the cellular level, which appear to be correlated with postoperative filtering function.