The Norwich Trabeculectomy Study: Long-term Outcomes of Modern Trabeculectomy with Respect to Risk Factors for Filtration Failure

Abstract

Objective: The aim of the study was to evaluate the long-term outcomes of a large series of ‘modern’ trabeculectomies with specific respect to traditional risk factors for failure. Methods: 636 consecutive ‘modern’, augmented ‘safe-technique’ trabeculectomies performed over an 11-year period (1998-2008) were assessed in a single centre, observational, cohort study. Traditional risk factors for failure (previous surgery, long-term exposure to topical medication, young age, secondary glaucoma and trainee surgeon) were assessed using various success outcome criteria. Success survival was defined with respect to various intraocular pressure (IOP) targets, using criteria for both complete and two categories of qualified success. A multivariate logistic regression analysis was performed to account for the significant number of patients with more than one risk factor. Results: The mean follow-up period was 65.5 (± 35.7) months. At final follow-up the mean IOP for all eyes was reduced from 23.4 (± 6.2) mmHg pre-operatively to 11.9 (± 4.2) mmHg (p<0.001) and the mean number of topical anti-glaucoma medications was reduced from 2.3 to 0.4 (p<0.001). Complete success rates were 65% (IOP ≤ 15 mmHg, no medications) and 71% (IOP ≤ 21 mmHg, no medications) at final follow-up. Qualified success rates varied from 78% to 97%, depending on IOP threshold. Outcomes for the various risk factor groups were compared with a ‘risk-free’ control group. Overall, traditional risk factors for failure did not significantly influence outcome for the various success criteria, but surgery performed by trainee surgeons had less satisfactory outcomes compared to surgery performed by a more senior surgeon. Clinic-based post-operative interventions were more frequently required in eyes with ‘traditional’ risk factors for failure. Conclusions: In a large cohort of mainly Caucasian patients, appropriately augmented, ‘modern’, ‘safetechnique’ trabeculectomy was highly successful and, together with ‘modern’ post-operative management, appeared to annul the effect of most ‘traditional’ risk factors for failure such as previous surgery, long-term exposure to topical medication, relative youth and secondary glaucoma.