title: Graft-free Ahmed valve implantation through a 6 mm scleral tunnel.
abstract: 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).
  
  
  METHODS
  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.
authors.affiliation: Faculty of Medicine, University of Manitoba, Winnipeg, Man. Electronic address: gdihgdih@gmail.com.
authors.forename: Gdih
authors.initials: G
authors.lastname: Gdih
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, B.C.
authors.forename: Kailun
authors.initials: K
authors.lastname: Jiang
mesh_terms: D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D005901:Glaucoma / Q000503:physiopathology / Q000601:surgery*; D020327:Glaucoma Drainage Implants; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D019919:Prosthesis Implantation / Q000379:methods*; D012189:Retrospective Studies; D012590:Sclera / Q000601:surgery*; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology*