Evidence-based medicine in glaucoma surgery

Evidence-based medicine (EBM) is a tool and guide for performing effective medical treatment. Here, as an example, EBM was applied to determine which between trabeculectomy and Baerveldt implant surgery would be more effective in a patient with a history of open-angle glaucoma. First, the author asked answerable clinical questions. Second, evidence using general search engines, such as the Cochrane Library or MEDLINE database, was collected. It was found that the Tube Versus Trabeculectomy (TVT) Study was a landmark study in determining optimum glaucoma surgical procedure. Third, the study's level of evidence was carefully examined. As the TVT Study was a prospective, randomized multicenter control study, its level of evidence was high. Fourth, the evidence to actual clinical decisions was applied, calculating the magnitude of the treatment effect using the results of the TVT Study. The event (surgical failure) rate in the control (trabeculectomy) and experimental (tube implant) groups (control event rate and experimental event rate, respectively) was obtained and the absolute risk reduction (ARR) was calculated by subtracting the experimental event rate from the control event rate. The inverse of ARR is the number needed to treat (NNT), which is the number of patients who must be treated to prevent a bad outcome. Using this method, it is possible to calculate the absolute risk (adverse event) increase (ARI) and the number needed to harm one more patient (NNH = 1/ARI). The balance of NNT and NNH is called the “likelihood of being helped and harmed.” The practice of EBM integrates clinical expertise of individuals with the best available external clinical evidence from systematic research.