Does It Matter Which Glaucoma Drainage Device Is Implanted?
The Tube Versus Trabeculectomy Study compared the Baerveldt® shunt to trabeculectomy1 . How do we know that other “tubes” work as well as the Baerveldt®? Could some of the other glaucoma drainage devices work even better?
Trabeculectomy with or without Mitomycin-C (MMC) appears to be more effective than placement of an Ahmed® device2 . On average the intraocular pressure (IOP) can be expected to be 3-5mmHg lower one year after trabeculectomy compared to one year after Ahmed® placement.
But time may erase such differences…
A systematic review of the higher quality glaucoma literature was published in 20053 . Surgical success was noted in about three quarters of cases around the two year mark. No significant differences were seen between the Molteno™, Baerveldt®, Krupin, or Ahmed® glaucoma drainage devices. Note, however, that surgical success was defined as an intraocular pressure (IOP) >5mmHg and <22mmHg. Few glaucoma surgeons today would consider an IOP above 18mmHg as successful so these results are likely higher than what would be experienced in clinical practice.
Another way to look at surgical effect is to evaluate percentage change in IOP. Here again, it appears that there is little difference between devices. On average, IOP was noted to drop between 51-62% from pre-operative measurements (according to the 2005 systematic review of the glaucoma literature).
1) Gedde SJ, Schiffman JC, Feuer WF, et al. Tube Versus Trabeculectomy Study Group. Treatement outcomes in the tube versus trabeculectomy study after one year of follow-up. Am J Ophthalmol. 2007;143:9-22.
2) Minckler DS, Vedula SS, Li TJ, et al. Aqueous shunts for glaucoma. Cochrane Database Syst Rev. 2006;(2):CD004918.
3) Hong CH, Arosemena A, Zurakowski D, Ayyala, RS. Glaucoma Drainage Devices: A Systemic Literature Review and Current Controversies. Surv of Ophthalmol. 2005;50(1):48-60.
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