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In an eye with a cataract, a combined surgery may be considered.įor a beginning surgeon, valved devices may be preferred as the surgical technique is simpler with localization to one quadrant without manipulation of the adjacent rectus muscles. The tube may be placed in the sulcus in a pseudophakic eye or pars plana in an aphakic, vitrectomized eye. The lenticular status of the eye should be noted. Gonioscopy should be performed preoperatively to determine the locations of peripheral anterior synechiae which may interfere with the tube insertion into the anterior chamber intraoperatively. Anterior chamber depth should be assessed to determine if tube insertion in the anterior chamber would be safe without touching the iris or cornea. The iris should be inspected under high magnification to detect neovascularization to consider preoperative use of anti-vascular endothelial growth factor (VEGF) agents to minimize intraoperative and postoperative bleeding. Clinicians should assess mobility of the conjunctiva to determine the best quadrant for drainage implant insertion. Recently, interest has increased in using these devices as a primary surgical procedure for uncontrolled primary open-angle glaucoma.Ĭareful preoperative examination and planning are essential for successful surgical outcomes. Additional indications include traumatic glaucoma, aphakic and pseudophakic glaucoma, post-keratoplasty glaucoma, and other secondary glaucomas. They are commonly used in the management of congenital and developmental glaucomas. In addition, the devices appear to be advantageous as a primary procedure in patients with a high likelihood of trabeculectomy failure, including neovascular and uveitic glaucomas. Glaucoma drainage devices have traditionally been reserved for patients with severe uncontrolled glaucoma who have failed previous glaucoma surgery. This review article will discuss the currently available glaucoma drainage devices, preoperative considerations and surgical technique, description and management of various complications, surgical outcomes in refractory glaucomas, comparative studies of various glaucoma drainage devices, and comparative studies of glaucoma drainage devices and trabeculectomy. Table 1 provides a summary of commercially available devices with their respective characteristics. The most commonly used valved implant is the Ahmed glaucoma valve, AGV (New World Medical, Rancho Cucamonga, CA, USA). Unlike the nonvalved devices, the valved or flow-restrictive devices allow only unidirectional flow from the anterior chamber to the subconjunctival space with a minimum opening pressure. The nonvalved devices include the Molteno (IOP, Inc., Costa Mesa, CA, USA, and Molteno Ophthalmic Limited, Dunedin, New Zealand), Baerveldt (Advanced Medical Optics, Inc., Santa Ana, CA, USA), Shocket, and Eagle Vision implants (Eagle Vision, Inc. In addition, other glaucoma drainage devices have been introduced and offer unique features designed to facilitate implantation, improve IOP control, and reduce acute postoperative hypotony.Ĭurrently, the glaucoma drainage devices are available in different sizes, materials, and design with the presence or absence of an IOP regulating valve. Since the introduction of the first glaucoma drainage device, Molteno implant, various modifications of the original design and improvements in surgical techniques over the past 40 years have led to greater success and lower complication rates. They also have demonstrated success in complicated glaucomas, such as uveitic glaucoma, neovascular glaucoma, and pediatric and developmental glaucomas, among others. These devices have shown success in controlling intraocular pressure (IOP) in eyes with previously failed trabeculectomy and in eyes with insufficient conjunctiva because of scarring from prior surgical procedures or injuries. Glaucoma drainage devices are designed to divert aqueous humor from the anterior chamber to an external reservoir, where a fibrous capsule forms about 4-6 weeks after surgery and regulates flow. 5.3 Comparative Studies of Glaucoma Drainage Devices and Trabeculectomy.5.2 Surgical Outcomes in Refractory or Difficult Glaucomas.5.1 Comparative Studies of Various Glaucoma Drainage Devices.3.1 Modifications To Prevent Hypotony with Nonvalved Implants.