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Ahmed glaucoma valve yields 78.7% overall success rate with few complications
Br J Ophthalmol. 2010;94:1174-1179.
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Standard implantation of a glaucoma valve effectively controlled IOP but was associated with a greater incidence of postoperative hypotony in pseudophakic or aphakic eyes, a study found.
"C3F8 gas and temporary Vicryl ligature is a useful technique for the prevention of postoperative hypotony when implanting the [Ahmed glaucoma valve] in high-risk eyes, for example, previous vitrectomy, aphakia or high myopia," the authors said.
The study included 94 eyes of 83 patients that underwent Ahmed glaucoma valve (AGV, New World Medical) implantation. One group comprised 51 high-risk eyes (50 aphakic or pseudophakic eyes and one phakic eye) that underwent implantation with gas fill and ligature. A second group included 28 phakic eyes that underwent standard AGV implantation. A third group included 15 pseudophakic or aphakic eyes that had standard implantation.
All three groups had similar preoperative IOP and number of medications. Mean postoperative follow-up was 28.9 months.
Study results showed an overall success rate of 78.7%. Mean IOP was reduced from 30.8 mm Hg preoperatively to 19.7 mm Hg at final follow-up. The at-risk group had markedly higher IOP at days 1 and 7 than the standard implantation groups. However, all three groups had similar IOP levels at final follow-up.
Medication use was significantly reduced in all three groups (P < .001).
Complications associated with postoperative hypotony were identified in six pseudophakic or aphakic eyes that underwent standard implantation. Corneal endothelial failure related to AGV implantation occurred in one eye in the at-risk group; the eye had aqueous misdirection with a flat anterior chamber.
Overall implant survival was 89.1% at 1 year and 72.9% at 4 years.
The authors present a retrospective analysis of a case series of patients who underwent implantation of an Ahmed glaucoma drainage device. Their results imply that use of C3F8 and temporary tube ligation in “high-risk” eyes reduced the rate of postoperative hypotony to an equivalent risk of eyes that are not high risk. There is some conventional thinking that Ahmed glaucoma drainage devices should not be ligated for fear of problems with the valve leaflets. The authors employed a way of temporarily restricting flow that may be useful in eyes in which immediate postoperative hypotony is of great concern.
– Douglas J. Rhee, MD
OSN Glaucoma Board
Member