Commissioning guides
Published 01 March 2012

Services for people at risk of developing glaucoma

This is an extract from the commissioning guide. The complete commissioning guide is available at www.nice.org.uk/guidance/cmg44

3 Assessing service levels for people at risk of developing glaucoma

Available data suggest that the indicative benchmark rate for new referrals to a service for the investigation of possible ocular hypertension (OHT) or suspected chronic open angle glaucoma (COAG) is 0.15% or 150 per 100,000 of the population aged 18 years or over per year.

The indicative benchmark for additional follow-up appointments for people with suspected COAG and OHT is 1.02% or 1020 per 100,000 of the population aged 18 years or over per year. Of these, at least 90% or 920 per 100,000 of the population will be people with OHT or suspected COAG who can be monitored in the community.

This service is likely to fall under the programme budgeting category 208X (problems of vision).

Use the service for people at risk of developing glaucoma commissioning and benchmarking tool to determine the level of service that might be needed locally and to calculate the cost of commissioning the service using the indicative benchmark and/or your own local data.

3.1 Assumptions used in estimating a population benchmark

The population benchmark is based on the following sources of information:

  • epidemiological data on the prevalence of OHT and suspected COAG

  • current practice – information on existing service provision

  • expert clinical opinion of the topic advisory group, based on experience in clinical practice and literature review.

3.2 Epidemiological data

The prevalence of OHT is estimated to be 3–5%[2] of people aged 40 or over (0.8–1.3 million people in England). OHT is a major risk factor for developing COAG[2]. Approximately 10% of UK blindness registrations are attributed to glaucoma. Around 2% of people older than 40 years have COAG[2], and this percentage rises to almost 10% in people older than 75 years[2]. This equates to around half a million people in England with COAG. The prevalence may be higher in people of black African or black Caribbean descent[3] or who have a family history[4] of glaucoma.

3.3 Current practice

There are limited published data on the number of people who are currently referred to services for the investigation of possible OHT, suspected COAG or COAG. Commissioners should use local data to inform discussion on optimum service levels.

In 2010/11 there were 11.9 million[5] NHS eye tests in England, which represented 69%[6] of all eye tests. If this figure is adjusted to include non-NHS eye tests it gives an estimated 17.2 million eye tests per year in England. Routine eye tests carried out by community optometric services are the main route for referral to the Hospital Eye Service or other consultant-supervised services for people with OHT or suspected COAG.

Analysis of Hospital Episode Statistics (HES) data for England in 2010/11 reveals that there were around 6.1 million outpatient attendances for the main specialty of ophthalmology. A proportion of these attendances will be for the investigation of OHT or suspected COAG.

It is estimated that there are around 60,000 new appointments for the investigation of possible OHT or suspected COAG per year in England. Repeat measures and/or referral refinement are likely to significantly reduce the proportion of people who need to be referred to the Hospital Eye Service or other consultant-supervised services for the further investigation and possible diagnosis of OHT, suspected COAG or COAG.

It is estimated that there are around 420,000 follow-up appointments for OHT or suspected COAG per year in England. It is estimated that 90% of people can have their OHT or suspected COAG effectively managed in the community. The new to follow-up ratio for investigation of OHT or suspected COAG is around one new case for every seven follow-up cases.

The 'Referral pathway diagram' worksheet within the commissioning and benchmarking tool provides a summary of the referral pathway for people at risk of developing glaucoma, including the numbers of people who may be managed within each stage of a service for people at risk of developing glaucoma.

3.4 Expert clinical opinion

The consensus opinion of the topic advisory group was that the number of people who are being referred to services for further investigation of possible diagnoses of OHT, suspected COAG or COAG, but who are 'false positives', has increased significantly in recent years. It is estimated that around 50% of all referrals for raised intraocular pressure (IOP) are false positives. This appears to be a result of increased referrals based on a single measure of IOP of over 21 mmHg made using non-contact tonometry[7]. The topic advisory group agreed that the increase in false positive referrals was undesirable and could be prevented by commissioning repeat measures and/or referral refinement services.

The consensus opinion of the topic advisory group was that referrals should be made to a service only when repeat measures have taken place. This is in line with quality statement 2 of the NICE quality standard for glaucoma:

'People with elevated IOP alone are referred to an appropriately qualified healthcare professional for further assessment on the basis of perceived risk of progression to COAG. There are agreements in place for repeat measures.' (Quality statement 2)

The consensus opinion of the topic advisory group was that commissioning a repeat measures scheme for people with raised IOP will reduce the number of false positives to around 33%. Within an optimal service configuration incorporating referral refinement this figure could reduce further to 20% or less.

For further information on specifying services for people with OHT or suspected COAG see section 4 on specifying services for people at risk of developing glaucoma.

The topic advisory group also agreed that future demand for services is difficult to quantify and subject to a high degree of uncertainty and local variation. Therefore, the benchmark presented here does not represent a steady state, and it may increase or decrease depending on the local flow of people with OHT or suspected COAG through the system and on demographic change.

3.5 Conclusion

Based on the epidemiological data and other information outlined above, it is concluded that the benchmark rate for new referrals to a service for the investigation of possible OHT or suspected COAG is 0.15% or 150 per 100,000 of the population aged 18 years or over per year.

The indicative benchmark for additional follow-up appointments for people with suspected COAG and OHT is 1.02% or 1020 per 100,000 of the population aged 18 years or over per year. Of these, at least 90% can be monitored in the community.

This benchmark is based on the following assumptions:

  • There are around 17.2 million routine eye tests by community optometric services each year. A proportion of people having a routine eye test will have raised IOP.

  • People with raised IOP will be referred to a service for the investigation and possible diagnosis of OHT, suspected COAG or COAG.

  • Around 60,000 adults are referred annually for the investigation of OHT or suspected COAG.

  • Repeat measures and/or referral refinement are likely to significantly reduce the proportion of people who need to be referred to the Hospital Eye Service or other consultant-supervised services for the further investigation and possible diagnosis of OHT, suspected COAG or COAG.

  • Additionally there are around 420,000 follow-up appointments for the investigation of OHT or suspected COAG each year, of which at least 90% can be effectively managed in the community.

The 'Referral pathway diagram' worksheet within the commissioning and benchmarking tool provides a summary of the referral pathway for people at risk of developing glaucoma, including the numbers of people who may be managed within each stage of a service for people at risk of developing glaucoma.

Commissioners should use their local needs assessment to determine optimum levels for local service provision. Commissioners should note that the benchmark rates do not represent NICE's view of desirable, or maximum or minimum, service levels.

Commissioners should use this benchmark and local data to facilitate local discussion on optimum service levels. There is considerable variation in the identification of people locally. This is influenced by the social, economic and demographic profile of the population, therefore commissioners are encouraged to consider local assumptions.

Use the service for people at risk of glaucoma commissioning and benchmarking tool to determine the level of service that might be needed locally and to calculate the cost of commissioning the service using the indicative benchmark and/or your own local data.



[2] National Collaborating Centre for Acute Care (2009) Glaucoma: diagnosis and management of chronic open angle glaucoma and ocular hypertension. London: Royal College of Surgeons.

[3] Leske C, Connell, A, Schachat, A et al. (1994) The Barbados eye study: prevalence of open angle glaucoma. Barbados Eye Study Group. Archives of Ophthalmology 112(6): 821–9.

[4] Nemesure B, Leske C, He Q et al. (1996) Analyses of reported family history of glaucoma: a preliminary investigation. Barbados Eye Study Group, University Medical Center at Stony Brook, NY, USA. Ophthalmic Epidemiology 3(3): 135–41.

[5] NHS Information Centre for health and social care (2011) General ophthalmic services activity statistics – England, year ending 31 March 2011.

[6] NHS Information Centre for health and social care (2006) Sight tests volume and workforce survey 2005–06.

[7] The College of Optometrists and The Royal College of Ophthalmologists (2010) Joint supplementary college guidance on supervision in relation to glaucoma-related care by optometrists. London: The College of Optometrists and The Royal College of Ophthalmologists.