Surveillance for ocular hypertension: an evidence synthesis and economic evaluation
Methodological quality of the review: High confidence
Author: Burr JM, Botello-Pinzon P, Takwoingi Y, Hernández R, Vazquez-Montes M, Elders A, Asaoka R, Banister K, van der Schoot J, Fraser C, King A, Lemij H, Sanders R, Vernon S, Tuulonen A, Kotecha A, Glasziou P, Garway-Heath D, Crabb D, Vale L, Azuara-Blanco A, Perera R, Ryan M, Deeks J, Cook J
Geographical coverage: Europe, United States of America (USA), Australia, Middle East
Sector: Glaucoma
Sub-sector: Ocular hypertension
Equity focus: None specified
Review type: Evidence synthesis and economic evaluation
Quantitative synthesis method: Meta-analysis
Qualitative synthesis method: Not applicable
Background: Monitoring patients at risk of developing glaucoma is crucial for prevention and early intervention. In 2009, the National Institute for Health and Clinical Excellence published guidelines for monitoring ocular hypertension (OHT). However, little data was available to guide best monitoring practice.
Objectives: The aim of the overall study was to determine effective and efficient monitoring criteria for OHT. Within the study, two systematic reviews were conducted. The following review refers to those and not to the larger study, as the SURE checklist would not be appropriate to critique the economic evaluation methodology.
Aim of systematic review one: to identify prediction models for the development of open angle glaucoma (OAG) that include intra-ocular pressure (IOP) as a predictor.
Aim of systematic review two: to compare the agreement, recordability, practicality, acceptability and reliability of the tonometers used in clinical practice using GAT as the reference tonometer.
Main findings:
Review one:
Several studies have identified potential risk factors for OAG, but there are few risk prediction tools that predict an individual’s likelihood of developing the disease over a specified period of time (e.g. five years). The review found only three models with published prediction equations. These models were derived using either the OHTS or the combined OHTS and EGPS populations. The OHTS-EGPS collaboration produced a model, the ‘means’ model, which was the most robust, and it is the model referred to as the OHTS-EGPS model. Unlike the OHTS model, this OHTS-EGPS model has not been validated in a different population by independent investigators.
All of the variables included in the models are or can be routinely collected in clinical
practice. A simple calculator based on the OHTS-EGPS model is available online and can be freely downloaded, enabling quick and easy estimation of the five-year risk of a patient with OHT developing OAG in at least one eye. A points-based system is also provided.
Review two:
This review was conducted to systematically evaluate the properties of a range of IOP measurement devices (tonometers) and their suitability to replace the current reference standard (i.e. GAT) for surveillance of patients with OHT in a primary-care setting.
They found 102 studies comparing eight candidate tonometer types against GAT. Studies included a variety of individuals, both patients and healthy subjects and patients with treated and untreated OHT and glaucoma. Poor reporting limited the assessment of the quality of the included studies.
Most studies did not provide sufficient details to assess all of the criteria. In particular, many studies did not state whether or not cases were consecutive, whether or not the tonometers were calibrated, if examiners were masked to results and the time period within which repeated measurements were taken. Despite comprehensive guidance being available on how to undertake measurement of IOP in clinical studies, a substantial proportion of studies appear to adopt sub-optimal practice, or at least reporting of such aspects.
The NCT or Perkins tonometer appears preferable if the aim is to achieve as close to a GAT measurement as possible. However, the findings cast doubt on the validity of GAT as the default standard. Consistent use of the same tonometer during clinical follow-up is arguably almost as important as the choice of tonometer.
The findings of this study support the clinical importance of establishing a true baseline IOP prior to initiating monitoring or treatment. IOP measurement using the NCT or hand-held applanation tonometer appears to give the closest agreement with GAT with > 75% of measurements within 3 mm Hg. The same type of tonometer should be used to compare IOP measurements in an individual.
The following studies were suggested by the authors: (a) a prospective cohort study including a representative sample of newly diagnosed OHT to update the risk prediction model and evaluate the optimal interval of serial glaucoma tests; standardisation of a measure of perimetry or optic nerve analysis with consensus on glaucoma conversion criteria; a comparison of alternative tonometers; costs and patient preferences for surveillance and treatment; and an updated economic model; (b) further development of tonometers to meet the needs of patients and the NHS.
Methodology: This study comprises three interlinked sub-studies. Two of the sub-studies include systematic reviews:
- Systematic review of prediction models estimating risk of progression to glaucoma.
- Evidence synthesis of the measurement agreement between alternative tonometers and the reference standard.
The SURE checklist has been applied only to the systematic review components and not to the larger economic evaluation study.
Applicability/external validity: The trial-based cohorts were a highly selected population, and therefore caution should be taken when generalizing results.
Geographic focus: All countries. There were results from low/middle-income settings.
Summary of quality assessment: Overall, there is high confidence in the conclusions about the effects of this study. Authors used appropriate methods to identify, screen and select studies for inclusion in the review, avoiding bias. Methods used to analyse findings were clear, and included studies were appraised appropriately.
