Purpose: 1. To describe the characteristics offiltering blebs after trabeculectomy in glaucoma treatment using anterior segment optical coherence tomography - Visante OCT. 2. To assess the association between characteristics offiltering blebs and intraocular pressure (IOP). Subject: 67 eyes of 67 glaucoma patients, who were operated (trabeculectoiny) and followed - up in Glaucoma Department, Vietnam National Institute of Ophthalmology from January 2010 to August 2010. Methods: Cross sectional description. The filtering blebs were evaluated by anterior segment optical coherence tomography - Visante OCT, Carl Zeiss Meditec - USA. Results: The filtering blebs of 67 eyes were studied, they included diffuse filtering 43. 3 percent, cystic 19.4 percent, encapsulated 25.4 percent and flattened 11.9 percent bleb types. There are significant differences between four groups in terms of height and reflectivity of the blebs, subconjunctival fluid collections, the route above and under the scleral flap and the drainage hole (p 0.05, p 0.01). 96.6 percent of eyes with diffuse filtering blebs and 84.6 percent of cystic filtering blebs have IOP reduced, higher than encapsulated blebs (47.1 percent) andflattened blebs (75.0 percent). The difference is significant with p 0.05 (Fisher's Exact Test). A significant correlation was found between IOP and the height, reflectivity, the route under the scleraflap with p 0.05.