Elbaklish KH, et al. - In this prospective and randomized clinical trial involving 56 patients, researchers contrasted a range of clinical outcome variables (intraocular pressure, glaucoma medications, visual acuity, and complications) between two Ahmed glaucoma valve (AGV) models (S2 and FP7). Participants with refractory glaucoma were randomly assigned to be implanted with either a polypropylene (S2) or silicone (FP7) Ahmed glaucoma valve. The data show that AGV's S2 and FP7 models were both effective in reducing IOP as well as minimizing the need for glaucoma medication. Though both of these AGV models had similar dimensions, they were made from different materials. However, after 12 months of follow-up, there were no significant clinical differences between the S2 and FP7 AGV groups. In addition, the data indicate that bleb encapsulation in both the S2 and FP7 groups was the primary factor responsible for failure rate and the need for glaucoma medication. The study further indicates that when viewed as a first-line therapy for cases undergoing trabeculectomy, the S2 and FP7 Ahmed valves are related to a high risk of failure.