The EX-PRESS™ Glaucoma Filtration Device (Alcon Laboratories, Inc., Fort Worth, Texas) has been commercially available in the United States since 2002 and was originally developed by Optonol, Inc. (Kansas City, Kansas) for implantation directly under the conjunctiva for an indication of control of intraocular pressure (IOP). It is a nonvalved, stainless steel device almost 3 mm long with an external diameter of approximately 400 microns and a 50 or 200 micron lumen, depending on the model. It has an external disc at one end and a spur-like extension on the other to prevent extrusion. The EX-PRESS™ shunt is one option for controlling IOP available to today’s glaucoma surgeon. The challenges and complications involved with EX-PRESS™ shunts are addressed below, as well as how to manage and prevent such scenarios. The original unguarded technique of implantation under the conjunctiva resulted in numerous complications, including hypotony, extrusion, and, most commonly, erosion of the implant. Typically, there was a period of hypotony followed by failure and erosion of the implant. Endophthalmitis has also been associated with an exposed implant. To avoid complications associated with subconjunctival implantation, Dahan and Carmichael proposed implanting the device under a scleral flap. This technique has greatly reduced erosions, and EX-PRESS™ shunts have been reported to have a lower rate of hypotony than trabeculectomy (15.8% with EX-PRESS™ shunt versus 22.5% in trabeculectomy). Since 2003, the manufacturer has recommended all users only implant the device under a scleral flap. Like all filtration surgery, failure is most commonly from episcleral and subconjunctival fibrosis. As with traditional filtration surgery, intraoperative adjunctive antimetabolites, such as mitomycin-C, may be used to limit the degree of postoperative scarring. However, should failure due to fibrosis occur, there are several options. The first is to add topical medications or perform laser trabeculoplasty. The second is to perform bleb revision or needling with an antifibrotic agent. Finally, as in a failed trabeculectomy, the surgeon may abandon the EX-PRESS™ shunt and perform a second unrelated procedure.
EX-PRESS glaucoma filtration device: Review of clinical experience and comparison with trabeculectomy
