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Kailun Jiang, Gdih Gdih; Graft-free Ahmed valve implantation through a 6mm scleral tunnel. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4746.
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To evaluate the safety, efficacy, and cost benefit to the health care system of Ahmed glaucoma valve (AGV) tube implantation through a 6mm scleral tunnel (graft-free technique).
Retrospective chart review (12-month follow-up) from a single clinical setting. Preoperative ocular medications, intraocular pressure (IOP), and visual acuity were compared to values recorded at each follow-up exam. The 95% confidence interval for fractional survival at any particular time was calculated using the Kaplan-Meier method. Failure was defined as: 1. IOP < 6mmHg or IOP > 21mmHg on 2 consecutive visits after 3 months 2. Additional surgical intervention to control IOP 3. No light perception (NLP) Eye banks across Canada were surveyed for cost incurred by the health care system for providing scleral tissue used in conventional AGV implantation.
84 eyes were implanted using the graft-free method with a success rate of 89.7% at 6-month. 6 eyes failed: 3 NLP, 1 persistent hypotony, 1 secondary AVG, 1 AGV extraction. The rate of hypotony peaked at 36% on post-operative-day (POD) 1, reducing to 20% by POD10 and 1.2% by 3 months. Clinical flat anterior chamber developed in 9.5% of eyes. 10% of eyes experienced a hypertensive phase (mean IOP=27.22mmHg). Preoperatively, eyes received on average 3 units of glaucoma medication. Postoperatively, 22 eyes required no medication for IOP control. Of the eyes requiring postoperative glaucoma medication, 40.5% restarted during week 3-4; an additional 23.8% of eyes were restarted 5-6 weeks post-operatively. By 6-month eyes were on average using 1.2-units of glaucoma medication. Hyphema was the most common (24%) early postoperative complication. The rate of conjunctival dehiscence within the first year is 1.2%. 4 eye banks from 4 provinces were surveyed for cost data. The cost of sclera ranged from $116 to $300 CAD. Using the graft-free technique, the cost of our surgical unit, excluding the cost of the valve, is 217% ($1872 CAD) less than that of the conventional scleral-graft method. This reflects the reduced number of instruments and OR time required for the graft-free method.
Our data suggests that the safety and efficacy of a 6mm scleral tunnel is comparable to conventional scleral-graft method. The graft-free scleral tunnel not only removes the risk of prion transmission, it simplifies and reduces procedural time and is a cost effective alternative to scleral-graft methods.
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