Frequency of visual field testing when monitoring patients newly diagnosed with glaucoma: mixed methods and modelling

Abstract

BackgroundVisual field (VF) tests are the benchmark for detecting and monitoring the eye disease glaucoma. Measurements from VF tests are variable, which means that frequent monitoring, perhaps over a long period of time, is required to accurately detect true glaucomatous progression. In 2009, guidelines for the diagnosis and management of glaucoma issued by the National Institute for Health and Care Excellence revealed an absence of research evidence about the clinical effectiveness and cost-effectiveness of using different monitoring intervals to detect disease progression. However, the European Glaucoma Society (EGS) guidelines on patient examination recommend that newly diagnosed glaucoma patients should undergo VF testing three times per year in the first 2 years after initial diagnosis.ObjectivesThe primary objective of this project was to explore the clinical effectiveness and cost-effectiveness of using different monitoring intervals to detect VF progression in newly diagnosed glaucoma patients. Other objectives sought to (1) explore glaucoma patients’ views and experiences of monitoring using focus groups; and (2) establish glaucoma subspecialists’ attitudes regarding frequency of VF testing using a five-item questionnaire.DesignThese questions were investigated using a multicentre audit of current practice and existing NHS data (VF records from almost 90,000 patients). New research knowledge was provided through statistical and health economic modelling of these and additional published data.ResultsThe multicentre audit showed that VF monitoring is, on average, carried out annually. Patient focus groups indicated that, although patients do not like VF testing, they accept it as a critical part of their care. Patients raised concerns regarding distracting testing environments, quality of instructions, explanation of results and excessive waiting times. Questionnaires revealed that clinicians’ attitudes towards the frequency of VF testing varied considerably, and many glaucoma specialists believed that current recommendations are impractical. Statistical modelling suggested that EGS recommendations could be clinically effective as progression can be identified sooner than is possible with annual testing. Health economic modelling suggested that increased VF monitoring may also be cost-effective [incremental cost-effectiveness ratio (ICER) was equal to £21,679].ConclusionsStatistical modelling of VF data suggests there is strong rationale for following EGS recommendations with the primary benefit of providing better information about fast-progressing patients. Our health economic model suggested that increasing VF testingmaybe cost-effective (ICER was equal to £21,679), especially when accounting for gains to society. Nevertheless, many clinicians consider increased VF testing of patients impossible with current resources. In addition, patient focus groups raised concerns about the practicalities of delivery of VF tests.Future workResults from this study could inform the design of a prospective randomised comparative trial of different VF monitoring intervals in glaucoma linked to stratifying patients according to risk factors for progression. The statistical model for VF data can be further developed to be used as a practical tool for optimising individualised follow-up. The views of clinicians and patients indicate that service delivery of VF testing is an important issue and worthy of further investigation. Ensuring the confidence and co-operation of the patient should be at the centre of future research into the most efficient strategies for glaucoma monitoring.FundingThis work was funded by the National Institute for Health Research Health Services and Delivery Research programme.

Are rates of vision loss in patients in English glaucoma clinics slowing down over time? Trends from a decade of data

“…Recent research evidence, reflected in clinical guidelines, has suggested that more frequent VF testing would help to identify rapidly progressing patients and this would have both clinical and potential health economic benefits. 32,33 At the same time, this would require a shift in resources, clinician opinion, and patient views about automated perimetry. 34,35 This study clearly shows a worse rate of VF loss was associated with older age and, albeit to a lesser extent, level of VF damage at diagnosis.…”

A view on glaucoma—are we seeing it clearly?

“…At the moment, certainly in England, there is a tendency to have a 'one size fits all' approach to monitoring the diagnosed patient. 18 We ought to think more about the use of monitoring resources in glaucoma, especially in those patients who present with more advanced disease as compared with those with little visual loss at diagnosis, or those with ocular hypertension only. Moreover, there appears to be a 'research obsession' with 'pre-perimetric' glaucoma and newer detection technology, but are these really required to prevent visual impairment?…”

“…16,17 Allocating perimetry resources correctly and installing perimetry at the centre of glaucoma follow-up is also a challenge. 18 Next, how do we best summarise visual field loss and the worsening of visual field loss? This is often done with a number (or series of numbers).…”

Combining optical coherence tomography with visual field data to rapidly detect disease progression in glaucoma: a diagnostic accuracy study

“…l Evaluation of patient experience and the clinical effectiveness and cost-effectiveness of including imaging outcomes with VF testing in managing patients with glaucoma. 12 Patient focus groups indicated that, although patients do not like VF testing, they accept it as a critical part of their care. This research explored the 'diagnostic gain' from including imaging data.…”

“…10,11 The requirement for frequent VF tests over extended periods of time results in delayed identification of vision loss and is a burden to patients and the NHS. 12 The vision loss in glaucoma is a consequence of structural damage to the ONH. 13 Nerve cells in the retina (retinal ganglion cells) transmit light sensitivity information to the brain through fibres that form a layer on the retinal surface, known as the RNFL.…”