Anatomic Considerations in the Implantation of the Ahmed Glaucoma Valve

Several aqueous drainage devices have been developed to treat refractory glaucoma. Among these are the Krupin, Molteno, Schocket, and Baerveldt implants. The recently introduced Ahmed glaucoma valve (Model S2, New World Medical, Rancho Cucamonga, Calif)1contains a pressure-sensitive silicone membrane valve that reduces postoperative hypotony and obviates the need for intraluminal stents or staged surgery. The single-plate implant has an oval polypropylene reservoir, measuring 16 mm in length and 13 mm in width. The manufacturer recommends placement of the implant at least 8 to 10 mm posterior to the limbus in the superonasal or superotemporal quadrant. We examined an eye enucleated for impending scleral perforation following a severe chemical injury. The eye had previously undergone placement of an Ahmed implant in the superonasal quadrant for uncontrolled secondary glaucoma. To our knowledge, this is the first report describing the pathological findings of an eye with an Ahmed implant. We also