Developing the intervention & outcome components of a proposed RCT of 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. This study develops the design for a randomised controlled trial (RCT) studying screening for OAG.

Screening may be a good way to find and treat more people who have OAG. Screening involves inviting everybody who has a particular characteristic, for example of a certain age, for testing. However, we need to know that screening will reduce the number of people losing vision and that it is value for money 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 can conduct a screening RCT we have to determine which screening tests should be evaluated, where testing should take place and who to include. Also we need to know how best to measure benefits and any harms of screening.

We will seek the views of people who do and do not have glaucoma, as well as views of health care professionals involved in providing eye care services.

Open angle glaucoma (OAG) is a primary, progressive optic neuropathy; the onset is asymptomatic, progression occurs silently until the disease is moderately advanced when vision is affected. Blindness due to OAG is irreversible. It is suggested that OAG may be a condition that fulfils the criteria for population screening. Two recent studies, based on economic modelling evaluations and reviews of the literature, suggest that screening in higher-risk groups might be worthwhile. Both these studies highlighted the considerable uncertainties in the available primary data and that further research is required to inform decisions on whether a screening programme should be initiated. A RCT is the optimal design to determine whether screening is effective, and no such RCT has been undertaken. Prior to initiating a RCT further research is required to inform the trial design, specifically the optimal screening approach and how outcome should be determined. This is what this proposed study aims to do.
A mixed method, multidisciplinary approach will be used to address the following research questions:
1. What screening strategy (i.e., test; site; target population; provider) will give the optimal combination of feasibility and acceptability to providers?
2. How feasible are the proposed identification strategies for each at-risk group and, given the results, what is the most appropriate unit of clustering?
3. What are the most likely effective interventions for maximising screening attendance by the targeted individuals?
4. What are the most appropriate methods for obtaining primary clinical and patient reported outcomes for use in the trial?

This research will deliver an acceptable screening strategy; feasible strategies to invite each of the target groups; informed trial design (unit of clustering); a decision as to whether a behavioural intervention might increase uptake of screening; an updated economic model to inform the RCT; defined trial outcomes. This research will thus enable a precise and evidence-based trial protocol to be developed that has the best opportunity to demonstrate the success or not of a glaucoma screening programme.

The study will be led from the Health Services Research Unit and the Health Economics Research Unit, University of Aberdeen and involves collaborators across the UK and Europe. The lead centre has long term infrastructure funding, making the ideal environment for undertaking this study and any definitive screening trial with long term follow up.