Recommendations for research
The guideline committee has made the following recommendations for research.
What is the predictive value of risk tools for identifying people in the community who are at increased risk of developing chronic open angle glaucoma (COAG) and identifying people with COAG who are at increased risk of sight loss?
Most cases of COAG are first detected by case-finding in community optometry after a sight test (with or without repeat measures, enhanced case-finding, or referral refinement). Identifying at case-finding which people are at high risk of conversion to COAG is important for guiding decisions about monitoring, treatment and referral. However, current evidence on the sensitivity and specificity of risk tools for developing COAG is of moderate-to-low quality, with all studies having a high or very high risk of bias. There was no evidence on cost effectiveness.
Similarly, a risk tool that identifies people with COAG who are at risk of progression to sight loss would be useful for both patients and healthcare professionals. People at higher risk of sight loss could have more frequent testing and perhaps more intensive treatment, whereas people at lower risk could have less frequent assessments and potentially less intensive treatment.
What is the clinical and cost effectiveness of treating an intraocular pressure (IOP) of 22 or 23 mmHg in people with normal optic discs and visual fields?
The only proven intervention for preventing and controlling glaucoma is lowering IOP. It has been widely accepted that the upper limit of statistically normal IOP is 21 mmHg. This was also accepted as the threshold for treatment, and most treatment studies aimed to achieve this target or a reduction in IOP of between 25% and 35% from baseline. However, more recently the Ocular Hypertension Treatment Study (OHTS) enrolled people with an IOP between 24 mmHg and 32 mmHg, but without glaucomatous optic nerve damage, to receive treatment or no treatment. The results showed a reduction in 5‑year incidence of very early glaucoma (either optic disc or visual field changes) from 9.5% in people not receiving treatment to 4.4% in those having treatment. This leaves an area of uncertainty about treatment for people with an IOP above 21 mmHg but below 24 mmHg. There are about 1.8 million people in the UK with an IOP of 22 or 23 mmHg. The costs associated with management in these people are sufficient to make this question of national importance.
What instrument should be used to measure health related quality of life in people with glaucoma?
Quality of life is the most important overall measure of treatment effect for patients as it measures their life experience and how their life experience is affected by interventions. Patient-reported outcome measures (PROM) are used for informing patients of the value of interventions and may affect their treatment choices. They also offer a tool for audit or service evaluation of glaucoma services, and for designing glaucoma trials.
However, uncertainty exists as to which PROM instrument should be used to measure outcomes of glaucoma interventions. A suitable instrument would be helpful to inform patients, healthcare professionals and policy makers about the effectiveness of glaucoma interventions. Identifying a valid and responsive PROM for measuring glaucoma outcomes would allow this instrument to be adopted in future clinical trials and glaucoma audits and would ensure meaningful comparisons between different interventions.
What is the effectiveness and cost effectiveness of optical coherence tomography (OCT) for diagnosing and monitoring glaucoma?
Glaucoma is an age-related chronic condition and the second leading cause of blindness in the UK. Once detected, glaucoma care usually takes place in hospital eye services, where patients are monitored for the rest of their life. There are over 1 million visits per year for glaucoma care in the NHS in England. This is predicted to increase substantially as a result of an ageing population and better detection in the community.
For diagnosis and monitoring, patients have an examination of the optic nerve and a review of visual field test results. Visual field testing has potential limitations: there is a learning effect and variability, it involves considerable patient effort, it is influenced by comorbidities, and in some people results are not reliable. Automated imaging with OCT overcomes many of these limitations.
OCT is an imaging technology that has evolved over the past 2 decades and is currently used in all NHS departments for the diagnosis and management of retinal diseases. However, current use of OCT and imaging technologies in glaucoma is highly variable.
It is possible the addition of OCT for diagnosing and monitoring glaucoma may enable earlier detection of disease and progression than when visual field testing is used alone. This could lead to escalation of treatment with less visual loss and blindness. However, it is possible that OCT may detect structural changes that will not be translated into functional loss, and may lead to unnecessary treatment. Overtreatment is likely to be associated with side effects and increased healthcare costs.
What is the effectiveness and cost effectiveness of the different models for glaucoma filtering (pathways from case-finding to assessment in secondary ophthalmic care) for detecting glaucoma and glaucoma-related conditions (ocular hypertension and suspected glaucoma)?
Routine optometric sight testing has poor sensitivity and specificity for detecting glaucoma and glaucoma-related conditions, resulting in a high percentage of false positive referrals to secondary care. These are costly for commissioners, cause unnecessary anxiety for patients and are a burden for secondary care. A variety of referral filtering models have been developed to improve the accuracy of referrals. These include 'repeat measures' schemes in which IOP measurement or visual field assessments, or both, are repeated at a separate visit; 'enhanced case-finding' referral enhancement schemes in which IOP measurements are repeated, detailed disc assessment is carried out and visual fields are performed with automated perimetry; 'referral refinement' schemes, which require tests sufficient for the diagnosis of ocular hypertension and suspected COAG, including gonioscopy, and the interpretation of these clinical findings.
Each scheme requires different levels of healthcare training and qualifications. Investment in equipment may also be needed to set up these services, and professionals would expect remuneration for providing these models of care.
It is unclear which of these models is the most accurate (sensitive and specific) and which is most cost effective. Evidence is therefore needed so that commissioners can commission the best services that allow accurate referral to secondary care for glaucoma assessment.