Frequency of visual field testing when monitoring patients newly diagnosed with glaucoma
Glaucoma is a disease of the optic nerve which can lead to irreversible loss of the visual field. Around 2% of people over 40 years old have glaucoma. Once diagnosed, patients need lifelong treatment and monitoring within the NHS. This represents a significant burden on NHS resources.
The clinical cornerstone of functional testing in glaucoma is the VF test on an instrument called a standard automated perimeter (SAP). Progression may be considered to have occurred when there is reliable evidence that VF damage has worsened significantly. Variability in measurement means that patients need several tests over a period of time before any change can be documented with confidence. If a change on VF is not detected there might be long-term costs associated with the disease progression following inadequate treatment; on the other hand, if patients are called in too often there is increased pressure on NHS resources.
The study involved a survey of current practice, and statistical and economic decision analytic modelling to identify follow-up schemes that could be subjected to a randomised controlled trial.
Outcome and Translation
Statistical modelling of VF data suggests there is a strong rationale for testing more frequently in the early period following diagnosis, with the primary benefit of providing better information about fast progressing patients. The economic model suggested increasing VF testing may be cost-effective, 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.
This project considered the clinical and cost-effectiveness of marginal changes to the current provision of glaucoma surveillance services. The results may impact on health outcomes and broader patient experience factors.
HERU researchers involved in this research project: Rodolfo Hernández (HERU/HSRU)
External Collaborators: D Crabb (City University); D Garway-Heath (Moorfields Eye Hospital); C Bronze and C Lemer (North Middlesex University Hospital Trust)
Crabb, D., Russell, R., Malik, R., Anand, N., Baker, H., Boodhna, T., Bronze, C., Fung, S., Garway-Heath, D., Glen, F., Hernández, R., Kirwan, J., Lemer, C., McNaught, A. and Viswanathan, A. (2013) Frequency of visual field testing when monitoring patients newly diagnosed with glaucoma. Final report submitted to NIHR Health Services and Delivery Research Program (Project number 10/2000/68).
Crabb, D., Russell, R., Malik, R., Anand, N., Baker, H., Boodhna, T., Bronze, C., Fung, S., Garway-Heath, D., Glen, F., Hernández, R., Kirwan, J., Lemer, C., McNaught, A. and Viswanathan, A. (2014) 'Frequency of visual field testing when monitoring patients newly diagnosed with glaucoma: mixed methods and modelling', Health Services and Delivery Research, 2(27).