Title: Study of technologies for the diagnosis of angle closure glaucoma (ACE)
Funder: Public Health Agency, NI

Abstract: Glaucoma is a chronic eye disease that damages the optic nerve, which carries visual information from the eye to the brain. It is the second leading cause of blindness in the UK, and responsible for 4,000 people being registered as blind or partially sighted each year. Many more have glaucoma that is not so severe, but which is bad enough to reduce their vision and quality of life._x000D_ ‘Open angle glaucoma’ is the most common type of glaucoma. ‘Angle closure glaucoma’ causes 1 in 6 glaucomas but is more severe than open angle. In an early stage, angle closure can be treated with laser to prevent glaucoma. The ‘angle’ is the front part of the eye that has drainage channels in it, where the aqueous humour -the clear fluid that fills that part of the eye– can drain out of. This helps prevent high pressure in the eye which is one of the key features of glaucoma. _x000D_ Angle closure is responsible for up to 20% of referrals to glaucoma services. Glaucoma UK’s helpline receives frequent calls for advice on angle closure and sends out over 8,000 angle closure patient information leaflets a year._x000D_ Patients with suspected glaucoma or angle closure are identified by community optometrists, who refer them to hospital eye services. Diagnosing glaucoma and angle closure is challenging and many people referred do not actually turn out to have a problem. This is a waste of NHS resources. Hospital eye services are very busy, dealing with nearly one in ten of all hospital outpatient attendances in the NHS. Glaucoma accounts for about a quarter of all outpatient activity, with over 1 million glaucoma-related visits per year._x000D_ The current NHS NICE guidance requires that patients who are referred to hospital eye services with possible glaucoma should have a test called ‘gonioscopy’ to examine the angle to rule out angle closure. This test needs to be done by an expert clinician with a special contact lens that touches the front of the eye. If there was an accurate non-contact assessment of the angle, gonioscopy by an expert clinician might not be needed for all individuals. These tests will reduce unnecessary hospital referrals and demand for clinician examination._x000D_ In the ACE study we will evaluate two different tests: (1) anterior-segment OCT, which is a sophisticated imaging technology that can be easily interpreted. This test is user friendly, easy to learn, fast, and provides consistent and high-resolution measurements of the angle structures. This device is widely available in NHS Trusts. (2) limbal anterior chamber depth test, that estimates indirectly if the angle is open or closed; it is simple and quick, and is done routinely by optometrists._x000D_ If one or both of the non-contact tests done by non-ophthalmologists are as accurate as gonioscopy, this would free up doctors time and NHS resources to treat more patients with eye diseases._x000D_ In our study, we will ask 600 people referred to 12 UK hospital eye services with suspected angle closure to have both tests. They will also be examined by an expert ophthalmologist, who will do gonioscopy unaware of the results of tests, so that we can find out how well the tests perform in an unbiased way. This will allow us to identify which is the most effective and efficient method of correctly diagnosing people with angle closure and which method represents best use of NHS resources. Our research team include clinicians, experienced researchers and two patients. Glaucoma UK and a PPI group will give advice.

Lay abstract: Research Question: What is the diagnostic performance of non-contact tests interpreted by optometrists (AS-OCT, LACD) or by photographers/imaging technicians (AS-OCT) for people referred to hospital with suspected angle closure?_x000D_ _x000D_ Background: Ophthalmology is the busiest hospital outpatient department in the NHS, and glaucoma accounts for 25% of its activity. Angle-closure is responsible for 1 in 6 glaucomas in the UK. Patients with suspected glaucoma require gonioscopy by an expert clinician to rule out angle closure. Use of alternative tests to diagnose angle closure will reduce the need for examinations by ophthalmologists._x000D_ _x000D_ Aims and Objectives: To evaluate the diagnostic performance and cost-effectiveness of two non-contact tests interpreted by optometrists (AS-OCT, LACD) or by photographers (AS-OCT) for patients referred to hospital with suspected angle closure compared to standard practice (gonioscopy by ophthalmologist)._x000D_ _x000D_ Design: Prospective, cross-sectional diagnostic study._x000D_ _x000D_ Setting: 12 NHS sites._x000D_ _x000D_ Target population: Adults with suspected angle closure._x000D_ _x000D_ Inclusion criteria: Adults referred from community optometry to hospital with suspected angle closure._x000D_ Exclusion criteria: Unable to provide informed consent._x000D_ _x000D_ Clinical pathways assessed: Individuals with suspected angle closure will undergo non-contact tests (AS-OCT, LACD) by optometrists and photographers/imaging technicians. If tests are positive patients will have gonioscopy by an expert clinician. If tests are negative patients will be discharged._x000D_ _x000D_ Primary outcome: Sensitivity of the new pathway to detect angle-closure._x000D_ Secondary outcomes: Specificity, positive/negative likelihood ratios, concordance, cost -effectiveness, proportion of patients requiring subsequent clinical assessment by ophthalmologist, proportion of patients unable to undergo tests and of tests of inadequate quality._x000D_ _x000D_ Sample size: 600 individuals who have been referred with suspected angle closure from primary care (community optometry). We will have a 95% probability of detecting the true sensitivity of either test to within ±3.5% based upon a sensitivity of 90%. The study will have a 95% probability of detecting the true specificity of either test to within ±5%, assuming a specificity of 75%._x000D_ _x000D_ Measures of costs & outcomes: Our hypothesis is that the new pathway will be highly sensitive and more efficient than standard care. Results of AS-OCT and LACD will be assessed separately. We will explore the accuracy of different thresholds and combination of tests. Sensitivity analysis will be done with multi-level logistic regression model._x000D_ _x000D_ Timetable: Pre-funding: Protocol development; Months 1-6: Site recruitment, ethics, HRA and R&D approvals, site training and initiation; Months 7-18: Patient recruitment, staggering centre start up; Months 19-24: Site close down, analysis and reporting._x000D_ _x000D_ Anticipated impact and dissemination: We will have more efficient hospital eye services. Our study will refine current NICE glaucoma guidelines and referral criteria. Our findings will be disseminated widely to those involved in the delivery and management of eye care services. We will have a knowledge exchange event at the end of the study, and publish via the HTA webpage and in specialist journals. The results will be presented at professional conferences and directly to patients via patient group meetings and the Glaucoma UK charity.

Research activity codes: 4.2 EVALUATION OF MARKERS AND TECHNOLOGIES;7.3 MANAGEMENT AND DECISION MAKING
Health categories: EYE