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Abstract
Background/aims To identify the percentage of those aged 65 and over who might be referred by community optometrists as ocular hypertensive suspects in the post-NICE era when differing guidance is followed by community optometrists.
Method The authors constructed an epidemiologically based model utilising Bridlington Eye Assessment Project (BEAP) data. Ocular hypertensive suspects' data were subjected to two algorithms (Association of Optometrists (AOP) and Joint College) to determine referral of suspects if community optometrists followed either algorithm.
Results 85 of 1643 people (5.2%) tested by BEAP, with normal acuity and visual fields, recorded Goldmann IOPs of >21 mm Hg in either or both eyes. Without pachymetric information, all 85 would be referred under the AOP algorithm, decreasing to 31 (1.9%) under the joint College algorithm (63% reduction). If central corneal thickness readings influenced referral, 39 (2.4%) would be referred under the AOP algorithm and 13 (0.8%) under the joint College algorithm.
Conclusion If community optometrists use Goldmann tonometry and pachymetry, following the joint College guidelines, referrals of OHT suspects could be reduced to a fifth of those under the original AOP guidance. Community optometrists should be encouraged to use GAT and pachymetry in order to refine referrals when another examination is normal. Potential savings to the NHS are considerable.
- Ocular hypertension
- epidemiology
- NICE
- BEAP
- intraocular pressure
- diagnostic tests/investigation
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In April 2009, the National Institute of Clinical Excellence (NICE) produced guidance on the diagnosis and management of chronic open-angle glaucoma and ocular hypertension (OHT) which included guidance to offer selected persons with OHT prophylactic drop treatment.1 Under the age of 65, this includes all those with an IOP>21 mm Hg and a central corneal thickness (CCT) of <555 μm. In those aged 65 and over and 80 and over, guidance is more complex with a series of threshold IOP and CCT readings at which treatment should be offered,
Almost immediately following publication of the NICE guidance, the Association of Optometrists (AOP) produced instructions to their members indicating that they should refer all people with a measured IOP of >21 mm Hg to an ophthalmologist for assessment. This led to a rapid and significant increase in glaucoma-related referrals to the Hospital Eye Service (HES) with many departments of ophthalmology recording over 100% increase in glaucoma related referrals. Referrals for raised IOP only had decreased in the previous 10 years as General Optical Council Guidance had changed permitting community optometrists to observe patients with a presumed diagnosis of OHT if the optometrist considered the individual to be at low risk of conversion to glaucoma. A web-based survey of referral practice post-NICE has suggested that, on average, each community optometrist is referring about four additional glaucoma-related referrals per month2 since the guidelines were published.
To assist workforce planning, we designed a study to estimate the number of OHT referrals to be expected from a population aged 65 and over. We would then be able to model the effect of a change of guidance on referral from primary care on the numbers of false-positive referrals (those who would not be offered treatment under NICE guidance).
Materials and methods
We utilised data from the Bridlington Eye Assessment Project (BEAP), a large-scale epidemiological study of eye disease in older people directed by one of us (SAV).3
Briefly, the project was a community-driven screening exercise for eye disease in patients aged 65 years and older. Subjects registered with all general practitioners in the town of Bridlington, England were systematically invited to attend an eye examination by one of four optometrists trained specifically for the project. Patients registered blind or partially sighted, bed-bound or suffering dementia, and those moving into or out of the area during the study were excluded.
A relevant standardised medical history was obtained (eg, diabetes, stroke, hypertension) together with the patient's drug and family history. Distance and reading spectacle requirements were recorded in addition to any history of amblyopia, ocular surgery or any other ocular disease. Specifically, any history of glaucoma was noted.
Patients then underwent a comprehensive eye examination including logMAR visual acuity testing (Bailey Lovie #4 Chart, National Vision Research Institute of Australia) and automated suprathreshold visual-field testing with the Henson Pro 5000 perimeter (Tinsley Instruments, Croydon, UK). A single-stimulus, supra-threshold central 26 point test was employed. This was automatically extended to a 68-point test if a defect was detected. Slit-lamp examination of the anterior segment was followed by measurement of intraocular pressure (IOP) utilising a calibrated Goldmann tonometer (GAT). CCT measurement was performed by ultrasound pachymetry (Tomey SP-3000 Pachymeter, Tomey Corporation, Nagoya, Japan). Gonioscopy was performed for those with narrow angles as suspected on van Herick testing and a dilated examination of the fundus followed utilising a 78 dioptre examining lens. This included a detailed optic-disc assessment with vertical cup/disc ratio estimation. Finally, Heidelberg Retina Tomograph II images (HRT II, Software Version 1.4.1.0, Heidelberg Engineering, Dossenheim, Germany) were obtained, and high-resolution digital fundus photographs (Topcon TRC NW6S, Topcon, Tokyo, Japan) were taken of the disc and macular area of each eye.
BEAP saw 3656 persons between November 2002 and January 2006. For the purposes of this study, individuals who would be referred under the AOP guidance as OHT suspects were defined as having the following characteristics (1) IOP greater than or equal to 22 mm Hg in either or both eyes, (2) normal visual fields in both eyes and (3) corrected logMAR acuity of at least 0.3 (Snellen equivalent 6/12) in both eyes. Exclusion criteria were (1) history of glaucoma, (2) use of ocular pressure-lowering treatment and (3) splinter haemorrhages observed clinically on the optic disc. No attempt was made to exclude patients on the basis of a neuroretinal rim configuration clinically suspicious for glaucoma. Informed consent was obtained from all participants, and a local ethics committee approved all methodology. All methods adhered to the tenets of the Declaration of Helsinki guidelines for research in human subjects.
Modelling based on two referral patterns was then performed. The first assumes all persons with an IOP of >21 mm Hg in either eye would be referred (AOP guidance), and the second assumes compliance with the joint College guidance on referrals published in December 2009.4
In addition, in order to examine the safety of the new College guidance, we reviewed the outcomes of the HES consultation(s) of all the BEAP OHT suspects. This included a further visual-field test and a comprehensive ocular assessment including GAT, gonioscopy and a dilated examination of the optic nerve head and fundus.
Results
One thousand six hundred and forty-three of the 3656 individuals examined in BEAP satisfied the entry criteria when the IOP criterion was disregarded, and within these 1643 people with ‘normal vision’, 125 eyes of 85 (5.2%) people recorded an IOP of >21 mm Hg. All subjects were Caucasian, and none were considered narrow-angle suspects by van Herick.
Considering the NICE cut-off with relation to CCT, 46 of the 85 eyes with the higher IOP of those individuals with at least one eye with an IOP>21 mm Hg had a CCT>554 μm (54%), and 69 of all the 123 eyes with an IOP>21 mm Hg had a CCT>554 μm (56%). Eighteen of the 31 people with an IOP>25 mm Hg in at least one eye had a CCT of >554 μm in the higher IOP eye (58%). None of the above percentages are significantly different from 50% (χ2 test).
Under the AOP guidance therefore, 85 people would have been referred to secondary care (5.2% (95% CI 4.1 to 6.2%)). This decreases to 31 (1.9% (95% CI 1.2 to 2.6%)) under the College guidance. If pachymetry is used to define those requiring referral (assuming a CCT of >555 μm negates referral until a measured GAT IOP of 25 mm Hg as per NICE), 39 people (2.4% (95% CI 1.6 to 3.1%)) would be referred under the AOP guidance and 13 (0.8% (95% CI 0.4 to 1.2%)) under the joint College guidance. Thus, the new joint College guidance, if followed, can be expected to reduce referrals in the over 65 age group by 63% without pachymetric assistance and 85% with it.
All 85 BEAP OHT suspects were reviewed by a consultant ophthalmologist in the HES as part of the BEAP protocol. All were asymptomatic. Twenty-two were confirmed as having OHT, two were considered to have narrow angles and underwent prophylactic bilateral peripheral iridotomies with a YAG laser, and three were considered to have preperimetric glaucoma (glaucoma without visual-field loss). In two of the three cases, the examining BEAP optometrist had recorded an abnormal disc suspicious for glaucoma (table 1).
Comparison of guidance from the Association of Optometrists and Joint College documents
Discussion
Community optometrists perform a valuable case-detection service in relation to glaucoma in the UK with >90% of new glaucoma patients being identified via routine optometric testing. Most (at least 80%) IOP testing in community optometry in England is performed utilising non-contact ‘air-puff’ tonometers.5 The largest UK study of the outcome of glaucoma referrals before the NICE guidance was released, indicated that a fifth of all referrals for suspect glaucoma were positive, with about a third having OHT and half being normal.6 In addition to the increase in glaucoma related referrals following the AOP's response to the NICE document,2 the HES has experienced an increased workload from advances in the treatment of wet age-related macular degeneration. In Scotland, community optometrists are now funded to refine their own referrals by retesting with GAT.7
This study estimates the reduction in referrals based on IOP alone to be expected in the over 65s if the joint College guidance on glaucoma referrals is followed by community optometrists in place of guidance originally distributed by the AOP and its associated bodies. In addition, it is of note that the use of pachymetry in primary care could further reduce referrals by 58%. That this figure is not greater than this is of interest, as it might be expected that, if CCT had played a major role in inducing a measurement of IOP of >21 mm Hg in an eye with ‘normal’ IOP, many more than 50% of those measuring an IOP>21 mm Hg by GAT would also have a CCT above the NICE cut-off. While many studies have found a significant tendency for measured GAT IOP to rise with increasing CCT, previous research from BEAP suggests than in the older Caucasian population, this tendency is not of great significance in eyes of normal subjects with only a 1.0 mm Hg mean increase in measured GAT IOP per 100 μm CCT increase.8
We did not exclude eyes considered to have suspect optic discs from the analysis, as all our subjects had dilated stereoscopic disc assessment by specially trained optometrists who may have a lower threshold for determining abnormality than the average community optometrist.
Following the introduction of targets in the NHS, new patients have taken preference over review patients when appointments for outpatient clinics are concerned. This has led to a phenomenon termed ‘the bow-wave of doom’9 where review patients have their appointments continually deferred forwards in time. In a condition such as glaucoma where asymptomatic loss of vision occurs, a review of status at frequent intervals is required to determine the presence of progression and to trigger a change of management.1 10 Preventable loss of sight has been reported as a result of the bow-wave phenomenon11 and unmeasured anxiety within patients and increased administration costs of organising changes of appointment add to the negative impact of unnecessary referrals.
GAT is now within the core competencies of community optometrists, and the technique of ultrasonic pachymetry is very easy to learn, although additional training may be required for some. This study demonstrates the reduction in referrals for specialist assessment that can be expected if all community optometrists used GAT with pachymetry and followed the joint College guidelines for referral. In England and Wales, in the year ending March 2009, 5 349 092 sight tests were performed on people aged over 60.12 Utilising population statistics13 to calculate the number in those aged 65 and over, we can estimate that 4 310 738 tests are performed in this age group. Assuming a similar prevalence of IOP measurements of >21 mm Hg as found in BEAP, at a local Nottingham PCT agreed 2010 tariff of £86.80 per new referral to ophthalmology, a saving of £16 463 570 could be made if the joint College guidelines are followed and pachymetry is used by community optometrists (assuming no additional costs for community tests).
Care should be taken not to extrapolate the results of this study to other populations of differing ethnicity in view of the different IOP and CCT profiles that may be encountered. In addition, although the only epidemiological study to report on the percentage of people recording an IOP of >21 mm Hg utilising non-contact tonometry found a similar percentage to the one in this study,14 if the majority of optometrists continue to use NCT for measuring IOP, the percentage and composition of OHT suspects may vary from those found in this study.
In conclusion, this study supports the position in Scotland where GAT and pachymetry are routinely performed by community optometrists in suspected OHT. Primary Care Trusts in other UK countries who fund glaucoma care should consider providing GAT devices and pachymeters to optometric practices within their boundaries and negotiate any additional charges payable for their use.
Footnotes
Funding The Bridlington Eye Assessment Project was funded by an unrestricted grant from Pfizer. We would also like to thank the following organisations for financial support of the Project: Pharmacia, Yorkshire Wolds & Coast Primary Care Trust, The Lords Feoffees of Bridlington, Bridlington Hospital League of Friends, The Hull & East Riding Charitable Trust, The National Eye Research Centre (Yorkshire), The Rotary Club of Bridlington, The Alexander Pigott Wernher Memorial Trust, Bridlington Lions Club, The Inner Wheel Club of Bridlington, Soroptimist International of Bridlington, and The Patricia and Donald Shepherd Charitable Trust.
Competing interests None.
Ethics approval Ethics approval was provided by the York Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.