- Design
- Retrospective clinical cohort study
- Population
- 186 eyes with failed trabeculectomy (94 repeat trabeculectomy, 92 Ahmed valve)
- Primary outcome
- Visual-field progression rate
- Effect
- Progression 31% vs 35% (P=0.6); trabeculectomy lower IOP and peak IOP; peak IOP risk 11% per mmHg
When a trabeculectomy fails, the surgeon must choose between another trabeculectomy at the same site and a glaucoma drainage device such as the Ahmed valve. This retrospective cohort compared the two on the outcome that matters most, visual-field progression.
Among 186 eyes (94 repeat trabeculectomy, 92 Ahmed valve), visual-field progression by two or more methods was similar (31% vs 35%, P=0.6), as were median rates of decline. Both lowered pressure, but repeat trabeculectomy achieved lower postoperative pressure and peak pressure and needed fewer medications. In the subset with preoperative data, trabeculectomy reduced the progression rate more than the valve compared with each eye's own baseline (P=0.03). Higher postoperative peak pressure, not mean pressure, carried an 11% higher risk of field deterioration per mmHg.
For practice this supports offering repeat same-site trabeculectomy rather than defaulting to a drainage device after a first failure, and it reframes the pressure target around controlling peaks, not just the mean.
- Retrospective comparison of 186 eyes: repeat trabeculectomy versus Ahmed valve after failed trabeculectomy.
- Visual-field progression was similar (31% trabeculectomy vs 35% valve, P=0.6).
- Repeat trabeculectomy gave lower postoperative and peak pressure and needed fewer medications.
- Trabeculectomy reduced progression more than the valve versus each eye's preoperative rate (P=0.03).
- Higher postoperative peak pressure raised deterioration risk 11% per mmHg; target peaks, not just the mean.
Why it matters
It counters a drift towards drainage devices after a first trabeculectomy failure and highlights peak pressure as the risk to target.
Don't overread it
This was a retrospective cohort; the similar progression rates do not prove equivalence, and the advantages of trabeculectomy could partly reflect patient selection.
The statistics, in plain English
A non-significant difference (P=0.6) means the two procedures looked similar for progression in this sample rather than proven equal; the pre-post comparison favouring trabeculectomy and the peak-pressure association are hypothesis-supporting given the retrospective design.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for ophthalmology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free