Evaluation of the conjuntival blebs using spectral domain optical coherence tomography after glaucoma surgery

Abstract

Objective: Analyze the application of the spectral domain optical coherence tomography (SD-OCT), Optovue iVue, on morphofunctional assessment of filtering blebs after different types of glaucoma surgery and point out the correlation between of morphologic features of blebs (bleb-wall thickness, scleral flap profile, and presence of hyporeflective spaces and internal cavity) and intraocular pressure (IOP). Methods: Thirty-eight eyes of thirty-two primarly open angle glaucoma patients, following three different types of glaucoma surgery (trabeculectomy with MMC 0.3%; with the implant of the Ex-PRESS device; with the insertion of Ologen [OLO]) were recruited. Patients attended a 6-month follow-up with intermediate checks at 1 week, 1 month and 3 months. Each visit include the evaluation of bleb using both slit lamp biomicroscopy and OCT. Results: In all patients, regardless of the type of surgery, a very significant reduction of IOP is observed after surgery. The bleb-wall thickness and the scleral flap profile are not shown to be sensitive parameters to identify the functionality of the bleb. The presence of hyporeflective spaces and of a cavity over the sclera is an important sign of bleb functionality. Among the different types of surgery, a higher percentage of blebs provided with hyporeflective spaces is in the Ex-PRESS group. In regards to the presence of a cavity over the sclera, there are no differences between the different groups. Comparing the blebs with filtering aspect at the OCT in the different groups, in the Ex-PRESS group there is a higher percentage of blebs with a filtering aspect compared to the other groups. Conclusions: Optovue iVue, is able to show detailed superficial features of the bleb which significantly correlate with the functionality of the bleb itself.