Graft-free Ahmed valve implantation through a 6 mm scleral tunnel

Objective: To evaluate the safety, efficacy, and cost savings of Ahmed glaucoma valve (AGV) tube implantation through a 6-mm scleral tunnel (graft-free technique). Design: Retrospective cohort study. Methods: The 95% confidence interval for fractional survival at any particular time was calculated using the Kaplan-Meier method. Failure was defined as (i) intraocular pressure(IOP) <6 mm Hg or >21 mm Hg or <20% IOP reduction on 2 consecutive visits after 12 months;(ii) additional surgical intervention to control IOP; or (iii) no light perception. Results: Eighty-four eyes were implanted with graft-free AGV with a success rate of 83% at 2 years. Fourteen eyes failed: 4 no light perception, 1 hypotony, 1 elevated IOP, 5 secondary glaucoma surgeries, 2 AGV extractions, and 1 corneal decompensation. The rate of transient hypotony peaked at 33% on postoperative day 1, reducing to 4% by 6 weeks. Transient flat anterior chamber developed in 8% of eyes. Eight percent of eyes experienced a hypertensive phase ( mean IOP = 28 mm Hg). Preoperatively, eyes received 3.8 units of glaucoma medication on average. Postoperatively, 8 eyes required no medication for IOP control. Of the eyes requiring postoperative glaucoma medication, 33% restarted during week 4; an additional 25% of eyes were restarted 6 weeks postoperatively. By 6 months, eyes were on average using 2.2 units of glaucoma medication. Hyphema (18%) was the most common early postoperative complication. The rates of conjunctival and scleral erosion by 2 years were 2.4% and 0%, respectively. Within our institution, excluding valve cost, there was a 39%-45% ($192-$376) cost reduction with the graft-free technique. Conclusions: The safety and efficacy of a 6-mm scleral tunnel is comparable to conventional scleral-graft method.