An ultrasound biomicroscopic study of filtering blebs after mitomycin C trabeculectomy.

Abstract

To investigate the relation between filtering bleb function and ultrasound biomicroscopic images, and to establish a new classification system for filtering blebs according to these images. After trabeculectomy with mitomycin C, the filtering blebs of 117 eyes from 117 patients with various types of glaucoma were examined using ultrasound biomicroscopy. Four parameters of the images-intrableb reflectivity, visibility of the route under the scleral flap, formation of a cavernous fluid-filled space, and bleb height-were correlated with the level of intraocular pressure (IOP). Reflectivity inside the bleb and visibility of a route under the scleral flap were highly associated with IOP control. Blebs were classified into four categories according to the four measured parameters: type L (low-reflective), type H (high-reflective), type E (encapsulated), and type F (flattened). Eyes with good IOP control had mainly type L blebs. Type E and type F blebs were seen mostly in eyes requiring additional medication. The structure inside a filtering bleb is visible by ultrasound biomicroscopy, and bleb function is significantly associated with its ultrasound biomicroscopic image in eyes trabeculectomized with adjunctive mitomycin C.