Outcome Measures in Glaucoma: A Systematic Review of Cochrane Reviews and Protocols.

Abstract

In clinical trials, the selection of appropriate outcomes is crucial for the assessment of whether one intervention is better than another. Selection of inappropriate outcomes can compromise the utility of a trial. However, the process of selecting the most suitable outcomes to include can be complex. Ideally, glaucoma trials aim to evaluate important outcomes for clinicians and patients. A high variability in the selection of outcomes suggests that there is no consensus on how best to evaluate the effect of glaucoma interventions. Further, it makes evidence synthesis difficult. The purpose of this review is to determine the extent of clinical outcome measures used in published glaucoma Cochrane Reviews and Protocols. A systematic review was conducted (up to February 2012) of all Cochrane Reviews and Protocols related to glaucoma interventions and published in English language. All clinical, patient-reported, as well as economic outcomes were included. In the Cochrane Library there were 12 Reviews and 9 Protocols on glaucoma. A total of 118 clinical outcomes were reported. Intraocular pressure was the most commonly used clinical outcome (n=40), and it was used in 11 Reviews and 5 Protocols. Intraocular pressure was evaluated in many different ways; the most common one was a composite definition of success. Safety outcomes were also frequently reported. Visual field progression or change was reported in 6 reviews and 3 protocols, but in 13 different ways. Patient-reported quality-of-life measures were chosen as main outcome measure in 1 Review. There is a large variability in outcomes selected in glaucoma Cochrane Reviews and Protocols. This heterogeneity in outcome selection impairs the ability for evidence synthesis. There is an urgent need for standardization of outcomes used in glaucoma trials.