Trabeculectomy Versus EX-PRESS Shunt Versus Ahmed Valve Implant: Short-term Effects on Corneal Endothelial Cells

We read the recent article by Casini and associates, entitled “Trabeculectomy versus EX-PRESS shunt versus Ahmed valve implant: Short-term effects on corneal endothelial cells,” with great interest. In their study they prospectively evaluated the changes in number, density, and morphology of the corneal endothelium cells in 128 eyes of 64 patients divided into 3 groups depending on the treatment received (trabeculectomy, Ahmed glaucoma valve, EX-PRESS implant). They found that the EX-PRESS shunt procedure compared to trabeculectomy and Ahmed glaucoma valve procedure showed no short-term effects (in 3 months) on corneal endothelial cells in patients with primary open-angle glaucoma.

The Ahmed glaucoma valve is one of the most commonly used drainage implants. However, in the long term it is reported to cause corneal decompensation in up to 30% of eyes, similar to our clinical experience. We evaluated the results of EX-PRESS mini glaucoma shunt implantation in a group of 15 post–penetrating keratoplasty (PKP) glaucoma cases unresponsive to medical antiglaucoma therapy in 2010. The indications for PKP were congenital glaucoma and bullous keratopathy in 6 cases (40.0%), pseudophakic bullous keratopathy in 2 (13.4%), perforated descemetocele in 3 (20.0%), regraft in 2 (13.4%), herpetic keratitis in 1 (6.6%), and keratoconus in 1 (6.6%). Eight of the eyes (53.3%) had undergone trabeculectomy and 2 (20%) had undergone glaucoma grainage device implantation before EX-PRESS shunt implantation. In 93.3% of these cases, the decrease in intraocular pressure (IOP) was 30% or above postoperatively. During a mean follow-up of 12.2 months (range, 8–19 months) neither biomicroscopic nor pachymetric findings displayed worsening in any of the grafts (clear grafts remained clear, and edematous grafts became clearer owing to IOP decrease).

The amount of endothelial cell damage triggered by the tube implantation is considered to vary according to the physical force during surgery and the area of contact during surgery and during postsurgery subsequent micromotion. As the EX-PRESS mini glaucoma shunt is a steel material, it is obviously more stable than the Ahmed glaucoma valve. Moreover, it probably is protected from the effects of eye movements because of its design (smaller and thinner external disc-like flange compared to Ahmed glaucoma valve). In addition, the shorter part of EX-PRESS being located in the anterior chamber compared to the other silicone material implants produces less endothelial damage. In all these properties the EX-PRESS tube surpasses others in terms of corneal endothelial cell preservation.

As a conclusion, EX-PRESS mini glaucoma shunt implantation is a good option not only for patients with low corneal endothelial cell density but also for post-PKP glaucoma patients who need to protect the clarity of their grafts.

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Jan 6, 2017 | Posted by in OPHTHALMOLOGY | Comments Off on Trabeculectomy Versus EX-PRESS Shunt Versus Ahmed Valve Implant: Short-term Effects on Corneal Endothelial Cells

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