Developing intervention & outcome components for a proposed RCT

The Glaucoma Screening Platform Study (GPS): Developing the intervention and outcome components for a proposed RCT on screening for open angle glaucoma.

Open angle glaucoma (OAG) is a common cause of blindness. Many people do not know they are developing OAG and miss out on the potential benefit of early treatment. Screening may be a good way to find and treat more people, but further knowledge is needed on whether it reduces the number of people losing vision compared with the current system of people choosing to attend for a sight test. To answer these questions we need a large, high-quality research study, i.e. a randomised controlled trial (RCT).

Before we could conduct a screening RCT we had to determine which screening tests should be evaluated, where testing should take place and who to include. We also needed to know how best to measure benefits and harms of screening. We sought the views of people who do and do not have glaucoma, as well as views of healthcare professionals involved in providing eye-care services.

The project included the update of an economic model and a full cost-effectiveness analysis.

Outcome and Translation

To make an evidence-based decision on screening for OAG a large RCT appears necessary. This study evaluated the feasibility of such a large study and identified the characteristics that successful screening strategies should have. It also addressed the question of whether such a proposed service could be evaluated. To our knowledge this is the first study using cost-effectiveness analysis to help in the definition of a complex intervention.

HERU researchers involved in this research project: Rodolfo Hernández

External Collaborators: A Azuara-Blanco, M Campbell, J Francis, A Green, JD Norie, C Ramsay (HSRU, University of Aberdeen); J Burr (University of St. Andrews); L Vale (University of Newcastle); RPL Wormald (Moorfield Eye Hospital) and D Crabb (City University)


Burr, J.M., Campbell, M.K., Campbell, S.E., Francis, J.J., Greene, A., Hernández, R., Hopkins, D., McCann, S.K., Vale, L.D. and Glaucoma Screening Platform Study Group (2011) 'Developing the clinical components of a complex intervention for a glaucoma screening trial: a mixed methods study', BMC Medical Research Methodology, 11, 54.

Burr, J., Hernández, R., Ramsay, C., Prior, M., Campbell, S., Azuara-Blanco, A., Campbell, M., Francis, J. and Vale, L. (2014) 'Is it worthwhile to conduct a randomized controlled trial of glaucoma screening in the United Kingdom?', Journal of Health Services Research and Policy, 19(1), 42-51.


Vale, L. and Hernández, R. (2010) 'Using economic evaluation to design and evaluate complex interventions', University of Newcastle, Newcastle, February 2010.

Burr, J. M., Azuara-Blanco, A., Campbell, M., Campbell, S., Francis, J., Greene, A., Hernandez, R., Hopkins, D., Prior, M., Ramsay, C. and Vale, L. (2010) 'Developing a population level complex intervention: Glaucoma Screening on Trial', 31st Meeting of the Society of Clinical Trials, Baltimore, 16-19 May 2010.

Hernández, R. and Vale, L. (2010) 'Review of glaucoma projects, their approaches and challenges', International Glaucoma Association, Health Economics Special Interest Group, Madrid, September 2010.