Molteno implant may yield better long-term IOP control than trabeculectomy

This prospective study compared long-term outcomes between Molteno implants and trabeculectomy when both procedures were performed as the first drainage operation in patients with primary open-angle glaucoma. It found the probability of IOP control after 10 years was better with the Molteno. Also, the failure rate was 3 percent in the Molteno group compared to 13 percent with trabeculectomy (failure defined as IOP > 21 mm Hg). However, caution should be used in extrapolating these results to the current standard of care.

Subjects included 695 patients who underwent surgery at a South African hospital between 1976 and 2007. Mean follow up was 7.7 years among 500 patients in the trabeculectomy group; and five years among 195 patients in the Molteno group. This long time course is interesting as is the large cohort, but it also makes the analysis more challenging due to heterogeneity. Only 2 percent of patients had trabeculectomy with mitomycin which clearly skews the results in favor of tubes. Also, the tube shunts were Moltenos, which changed over the course of this study from a single to a double plate design.  

While it's interesting to compare these results with the Tube vs Trabeculectomy Study (TVT), because the population and selection criteria were similar, there are some notable differences. Baerveldt tube shunts were used exclusively in the TVT study, while this study used Moltenos. Also, mitomycin C or 5-fluorouracil was used in only 2 percent of trabeculectomies and none of the implants. Threatened bleb fibrosis was treated with oral anti-inflammatory fibrosis suppression in this study; whereas in the TVT, all trabeculectomies included application of mitomycin C.

Additionally, far more TVT patients had previous cataract surgery compared to this study - 80 percent vs. 2 percent in the trabeculectomy group and 78 percent vs. 11 percent in the implant group. Also, 18 percent of this study's patients who had trabeculectomy and 24 percent who had implants had cataract extraction at the time of the glaucoma surgery, and a higher percentage of this study's patients had pseudoexfoliative glaucoma -  23 percent vs. 1 percent in the trabeculectomy group and 38 percent vs. 7 percent in the implant group.

Overall, results with respect to IOP control were similar to the first three years of follow-up in the TVT in that the implant groups had higher success rates compared with trabeculectomy, but there are notable differences between these two studies.