The United Kingdom Glaucoma Treatment Study: a multicenter, randomized, placebo-controlled clinical trial: design and methodology

Abstract

Objective: Elevated intraocular pressure (IOP) is a major risk factor for the deterioration of open-angle glaucoma (OAG); medical IOP reduction is the standard treatment, yet no randomized placebo-controlled study of medical IOP reduction has been undertaken previously. The United Kingdom Glaucoma Treatment Study (UKGTS) tests the hypothesis that treatment with a topical prostaglandin analog, compared with placebo, reduces the frequency of visual field (VF) deterioration events in OAG patients by 50% over a 2-year period.

Design: The UKGTS is a randomized, double-masked, placebo-controlled, multicenter treatment trial for OAG.

Participants: Five hundred sixteen newly diagnosed (previously untreated) patients with OAG were recruited prospectively at 10 centers between 2007 and 2010.

Methods: Patients were assigned by concealed telephone allocation to treatment with a prostaglandin analog (latanoprost 0.005%) or placebo. The observation period was 2 years, with subjects monitored by VF testing, quantitative imaging, optic disc photography, and tonometry at 11 visits. Data were acquired according to novel protocols optimized for the analysis of deterioration velocity. The sample size was determined for a 2-sided error of α=0.05 to detect the difference between 24% and 11% in incident deterioration over a 24-month follow-up at 90% power and assuming a 25% attrition rate.

Main outcome measures: The primary outcome was time to VF deterioration within 24 months. Secondary outcomes included the deterioration velocity of VF and quantitative imaging measures and the relationship between these velocities and risk factors for deterioration.

Results: The study design enabled a short trial with a 2-year observation period and provided data that can be used to assess the feasibility of further shortening trial duration with the progression velocity of VF and structural imaging measurements as outcomes.

Conclusions: The UKGTS is the first randomized, placebo-controlled trial to evaluate the efficacy of medical treatment in reducing VF deterioration in OAG. The measurement of deterioration velocity and inclusion of quantitative imaging has the potential to reduce the number of patients and duration required for subsequent clinical trials. This trial also will quantify risk factors for deterioration, enabling more precise risk profiling of patients and the development of patient management protocols.

Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.