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Editors Selection IGR 23-2

Surgical Treatment: Trabeculectomy vs. Drainage Devices

Comment by Angelo Tanna on:

Casini et al. used specular microscopy to prospectively investigate the impact of trabeculectomy (n = 22), the ExPress Shunt procedure (n = 24) and Ahmed drainage device surgery (n = 18) on corneal endothelial cell number, density and morphology at one and three months after surgery compared to of 32 fellow eyes that were on medical therapy and had no prior incisional glaucoma surgery. The authors found small but statistically significant reductions in corneal endothelial cell density at three months in the trabeculectomy group (4.2%, p = 0.007) and in the Ahmed drainage device group (3.5%, p = 0.04); however, there was no significant change in the ExPress group.

Although performed prospectively, eyes were not randomized to the different surgical interventions. A confounding factor may lie in the fact eyes that had deep anterior chambers underwent ExPress Shunt implantation and other eyes (presumably with shallow anterior chamber angles underwent trabeculectomy.

Eyes that undergo ExPress shunt implantation usually do not experience flattening of the anterior chamber during surgery. With trabeculectomy, however, the anterior chamber is likely to be flat at some point during creation of the fistula if measures to avoid this are not undertaken, including use of an anterior chamber maintainer or intracameral viscoelastic, the use of pre-placed scleral flap sutures, and the creation of a small, valved corneosclerostomy. The authors do not specify the details of their surgical techniques nor do they specify whether the anterior chamber was flat in any of the study eyes during the procedure.

Wagschal et al. previously reported the results of a prospective clinical trial that studied endothelial cell density in 64 eyes that randomized to trabeculectomy or the ExPress Shunt procedure and found no significant difference from baseline or between groups at one year.² Controversy remains as to whether there is a difference in the impact on the corneal endothelium with the ExPress Shunt versus trabeculectomy, therefore, further studies are needed.

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