EYcacy and safety of the Ahmed glaucoma valve implant in Chinese eyes with complicated glaucoma

Aims—To evaluate the eYcacy and safety of the Ahmed glaucoma valve implant in Chinese eyes with complicated glaucomas. Methods—This retrospective study reviewed the final intraocular pressure, visual outcome, and incidence of complications in all patients with the Ahmed glaucoma valve implant performed at the Prince of Wales Hospital, Hong Kong, between June 1996 and November 1998. Results—A total of 65 eyes from 60 patients were treated with the Ahmed glaucoma implant. At a mean follow up (SD, median) of 21.8 (9.2, 28.0) months (range 6–37 months), the mean intraocular pressure was reduced from 37.0 (SD 12.1) mm Hg before the implant surgery to 16.1 (12.4) mm Hg at the last follow up after surgery. The success rate of intraocular pressure control of <22 mm Hg was achieved in 73.8% of operated eyes. Transient postoperative hypotony with shallow anterior chamber occurred in 10.8% of cases. The most common postoperative complication was the formation of encapsulated bleb (24.6%). Conclusions—The Ahmed glaucoma valve implant appears to be eVective and relatively safe for treating complicated glaucomas in Chinese eyes. The success rate is comparable with those reported in nonAsian eyes. Formation of postoperative encapsulated bleb is, however, more commonly encountered. (Br J Ophthalmol 2000;84:718–721) Glaucoma drainage devices (GDD) provide an alternative treatment in complicated and refractory glaucoma cases. A GDD with valve is designed to reduce the incidence of postoperative hypotony. The Ahmed glaucoma valve (AGV) implant (New World Medical, Rancho Cucamonga, LA, USA) was introduced in 1993. It has a built in Venturi valve, which oVers a set resistance to the aqueous outflow. A folded silicone elastomer membrane forms the valve with its free edge forming a one way outlet. The valve will open at a specific level of intraocular pressure (IOP), thus reducing the chance of hypotony in the early postoperative period. Initial clinical experiences with this implant have demonstrated that postoperative hypotony was less common than the nonvalved GDD. However, the valve may be a potential site for obstruction by inflammatory debris, especially in Asian eyes that are known to have more severe tissue reactions than white people. 11 Aung and Seah reported good outcome of GDD in Asian eyes. However, the GDD used in their series were non-valved (Baerveldt and Molteno glaucoma implants). Huang and associates reported good eVectiveness of the AGV implant in their series but the majority of their patients were non-Asian and racial diVerence was not taken into account in their risk factor analysis. Only little information regarding the safety and eYcacy of the valved glaucoma drainage implant in the treatment of refractory glaucoma in Chinese eyes is available in the literature. This retrospective study aims at reviewing the surgical outcome in terms of the IOP, visual acuity, and incidence of complications in all patients receiving AGV implant surgery at the Prince of Wales Hospital, Hong Kong, between June 1996 and November 1998. Patients and methods A retrospective review of the records of all patients who received AGV implant surgery for glaucomas not responsive to medical and nonimplant surgical treatments in the specified period was performed. All surgeries were performed by two of us (JSL and DSL) and no other GDD were used during the study period. The superotemporal quadrant was used for the implant fixation in all eyes. For aphakic patients, anterior vitrectomy was performed before AGV implant was fixed. A fornix based conjunctival flap and Tenon capsule was dissected to allow insertion of the plate of the implant into the sub-Tenon space 8 mm behind the corneal limbus. Before insertion of the plate, the valve of the implant was primed by irrigating the lumen of the tube with balanced salt solution (BSS, Alcon, Fort Worth, TX, USA). The plate was fixed to the sclera with two 9-0 black nylon sutures (Ethicon, Ethilon). The tube was shortened to the desired length with its sharp bevel facing anteriorly. An anterior chamber (AC) paracentesis wound was created at the peripheral cornea and sodium hyaluronate 1% (Healon, Pharmacia and Upjohn) was injected to prevent sudden collapse of the AC when the sclerostomy was made. The tube of the implant entered the AC parallel to the iris plane through the sclerostomy made with a 23 gauge syringe needle. The tube was fixed to the sclera with one 9-0 black nylon suture. The anterior Br J Ophthalmol 2000;84:718–721 718 Department of Ophthalmology and Visual Sciences, the Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, NT, Hong Kong