All procedures was performed by glaucoma specialists under general anesthesia employing the same technique in all subjects. The surgical field was prepared and draped in the usual sterile fashion. After insertion of a lid speculum and irrigation with povidine iodine 5% solution, a 7-0 silk limbal traction suture was placed to rotate the globe and achieve optimal supratemporal exposure. A limbus-based conjunctival peritomy was created 4mm posterior to the limbus and Tenon's capsule was dissected using Westcott and Stevens scissors. Hemostasis was achieved using wet field bipolar cautery. The Ahmed Glaucoma Valve (AGV) plate was secured to the sclera 8 mm posterior to the limbus with two interrupted 7-0 silk sutures. The tube was trimmed to an appropriate length with the bevel facing anteriorly and inserted into the anterior chamber through a corneoscleral track created with a 23-gauge needle. The tube was fixed to the episclera with a 10-0 nylon mattress suture. A quadrangular donor scleral patch graft (4×7 mm) was fashioned to cover the exposed part of the tube and was secured to the sclera using 10-0 nylon sutures. At this stage, in adjunctive triamcinolone group, 10 mg triamcinolone was injected in the subtenon space around the Ahmed Glaucoma Valve (AGV) plate. The conjunctiva and Tenon were closed using 10-0 nylon suture in a running fashion. At the end of the procedure, a subconjunctival injection of 4 mg betamethasone and 50 mg cephazolin were given in all eyes.
All patients were examined on the first post-operative day; the postoperative regimen included topical chloramphenicol 0.5% eye drops 4 times per day for 1 week and topical betamethasone 0.1% eye drops 6 times per day which was tapered over 6 to 8 weeks, except in cases with severe inflammation which required a longer period of treatment.
Follow up examination was repeated every week during the first month and thereafter at 6 weeks, and 3, 6, 9 and 12 months after the operation. Possible complications such as endophthalmitis, choroidal effusion or hemorr, wound leakage, hyphema, hypotony, malignant glaucoma, implant exposure, tube malposition, bleb encapsulation, and decreased best corrected visual acuity (BCVA) more than 2 lines were mentioned. IOP was measured by a calibrated Goldmann applanation tonometer (SN-9007, Haag-Streit, Koniz, Switzerland). All measurements were obtained by one masked examiner.
The main outcome measure of the study was intraocular pressure and number of anti-glaucoma medications. Complete success was defined as IOP between 6 and 21 without the use of any glaucoma medication. Partial success was defined as IOP between 6 and 21 with a maximum of 2 glaucoma drops. Overall success rate was the sum of complete and partial success rates. Failure was defined as IOP\>21, IOP\<21 with ≥3 medications, loss of vision, shunt extrusion and need for additional glaucoma surgery. Other outcome measures included best corrected visual acuity (BCVA), number of glaucoma medications, and complications.
