Although during 5 years the IOP decreases equally in previously operated eyes undergoing surgery for Baerweldt shunt and trabeculectomy, the success rate after shunt operation seems be better.
Systematic review
Information was insufficient to conclude whether there are differences between aqueous shunts and trabeculectomy for glaucoma treatment. While the Baerveldt implant may lower IOP more than the Ahmed implant, the evidence was of moderate-certainty and it is unclear whether the difference in IOP reduction is clinically significant. Overall, methodology and data quality among existing randomized controlled trials of aqueous shunts was heterogeneous across studies, and there are no well-justified or widely accepted generalizations about the superiority of one surgical procedure or device over another «Tseng VL, Coleman AL, Chang MY ym. Aqueous shunts ...»1.
Tube Versus Trabeculectomy (TVT) study
The 3-year results of the Primary Tube versus Trabeculectomy (PTVT) –study was published in 2020. Previously 242 unoperated eyes of 242 patients where randomized into two groups: 125 eyes for Baerveldt 350 mm2 shunt and 117 eyes for trabeculectomy. Failure of surgery was defined as 1) IOP > 21 mmHg, 2) less than 20% reduction from pre-operative IOP, 3) IOP < 5 mmHg, 4) re-operation for glaucoma, or 5) loss of light perception. The cumulative probability of failure was similar in both groups (33% in Bareveldt group, and 28% in the trabeculectomy group; HR 1,39, 95% CI 0,9-2,2, p=0.17). However, lower IOP was achieved in the trabeculectomy group than in the Baerveldt group (12.1 ± 4,8 vs. 14.0 ± 4.2 mmHg; p=0.008) with less medications (1.2 ± 1.5 vs. 2.1 ± 1.4, P<0,001).