AIM:To analyze the features of the filtering blebs following implantation of the Ex-PRESS glaucoma device (model P-50) with the aid of the Visante anterior segment optical coherence tomography (AS-OCT)METHODS: Five patients with open angle glaucomas were included in the study. They all underwent implantation of the Ex-PRESS device under a scleral flap. The surgical procedure was augmented with the use of mitomycin C subconjunctivally. The filtering blebs were analyzed with the Visante AS-OCT with the scans taken along the axis of the implantation of the glaucoma device.RESULTS: All filtering blebs were graded as diffuse functioning. The morphological characteristics of the blebs were similar to those of the trabeculectomy. However the use of the Ex-PRESS implant tend to form a characteristic episcleral lake at the site of the plate of the implant.CONCLUSION: The use of the Ex-PRESS implant produces filtering blebs similar to those of the trabeculectomy with the formation of a characteristic episcleral lake at the site of the plate of the implant.