Why 'the more the merrier' doesn't apply to glaucoma monitoring

Though ocular hypertension may be the only modifiable risk factor for glaucoma, the second-leading cause of sight loss in the United Kingdom, monitoring for ocular hypertension more than twice a year is not efficient, researchers said.

 “We find no clear benefit in terms of cost-effectiveness from intensive monitoring of people with ocular hypertension to detect glaucoma,” reported researchers from the University of Aberdeen, University of St. Andrews, and New Castle University. They published the finding in the British Journal of Ophthalmology.

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But guidelines of the UK National Institute for Health and Care Excellence (NICE) calling for long-term monitoring of ocular hypertension have raised the concern that they might “overwhelm healthcare and patients,” they wrote.

To test the efficacy of this kind of monitoring, they developed a model to simulate a cohort of 10,000 people in the United Kingdom with confirmed ocular hypertension defined as an IOP over 21 mm Hg and no clinical signs of glaucoma.

Five scenarios were compared for monitoring and treating IOP:

1)    Biennial Secondary: Monitoring twice a year in an eye-care setting led by a consultant. Treatment with prostaglandin analogue initiated when the baseline risk of glaucoma was at least 6% based on a 5-year risk estimator (Ophthalmology. 2008; 115:2030-2036). Responsiveness assessed at 2 months with less than a 15% reduction in IOP prompting the addition of a topical beta-blocker.

2)    Biennial Primary: Monitoring twice a year in primary care led by a glaucoma-trained optometrist or general practitioner. Treatment as in scenario 1.

3)    Treat All: Monitoring annually by a community optometrist. Treatment initiated without reference to glaucoma risk stratification. Treatment per NICE guidelines (based on age, central corneal thickness (CCT) and IOP).

4)    NICE Intensive: Monitoring every 4 to 12 months by a glaucoma-accredited professional in either a consultant-led hospital or community optometry. Treatment as in scenario 3.

5)    NICE Conservative: Monitoring every 6 to 24 months. Treatment as in scenario 3.

Results of the study

The mean age of the simulated population was 57 years. The mean IOP was 25 mm HG. Each simulated individual had a glaucoma risk based on the natural history of open-angle glaucoma estimated from the distribution of predictors in a population of European ancestry.

The researchers incorporated data from systematic reviews on the variability in IOP measurements and visual field indices. And they assumed that treatment adherence was 75% except in the “Treat All” scenario, where they assumed 50%.

The researchers derived cost and utility data from the British National Formulary and data from 225 people with glaucoma valued using UK population tariffs.

They estimated that the risk of patients converting to early glaucoma ranged from 21% to 23% depending on the scenario.

Analysis and conclusion

The “Treat All” scenario was the least costly and also the least effective. The “NICE Intensive” group was the most effective but the most costly. In general, the authors said, the NICE scenarios were less cost effective than the alternatives they designed.

Adding quality of life years gained made little difference, they said.  “Initiating treatment as soon as [ocular hypertension] is identified with minimal monitoring once the target IOP is reached is the least costly approach, and compared with the alternative pathways modeled could be seen as the most cost-effective,” they wrote.

As an alternative, initiating treatment if the 5-year glaucoma risk was more than 10%, minimizing the cost of repeat eye-care visits, and supporting patient adherence to treatment, with subsequent glaucoma tests every 2 years could be an efficient approach for glaucoma surveillance, the researchers found.

“The feasibility of alternative and more affordable monitoring pathways should be explored,” they concluded.

J.M. Burr, MD

e: jmb28@st-andrews.ac.uk