retinopathy is the leading cause of blindness of patients of working age
in the UK and represents a significant workload for the health services.1
Currently at least 2% of the UK population are known to have diabetes,
of whom 10-13% have sight-threatening diabetic retinopathy.2-4
is widely accepted that screening for diabetic retinopathy represents both
good clinical practice and cost-effective healthcare. The natural history
of the disease is known, and early detection and treatment of retinopathy
has been shown to be effective in preventing visual impairment.5-6
With appropriate medical and ophthalmological intervention, including good
glycaemic and blood pressure control, it has been estimated that blindness
may be prevented in at least one ye in 60-70% of cases with maculopathy
and 90% of cases of proliferative retinopathy. The disability caused by
blindness and partial sight, as well as the social costs in terms of loss
of earning capacity and the required social support are considerable.7
Lack of screening may also result in costly compensation claims. The recent
debate has focused on what is the most suitable screening test to use.
FOR DIABETIC RETINOPATHY SCREENING
performance of a screening system may be judged by its sensitivity (the
ability to detect true positives) and its specificity (the ability to detect
true negatives) as well as on it s practical and financial implications.
The British Diabetic Association (Diabetes UK) has established standards
for any diabetic retinopathy screening programme of at least 80% sensitivity
and 95% specificity. An effective screening service needs to have a systematic
call and recall of eligible patients, trained professionals, recorded outcomes
with targets and standards, and quality assurance. Promotion of uptake
of the screening programme, and efficient and appropriate follow-up of
those with retinopathy are also important features.
is important not only for the detection of sight-threatening retinopathy,
but also for the detection of any retinopathy so that particular effort
can be made to improve blood pressure and glycaemic control.
there is great variation in the provision of diabetic retinopathy screening
services throughout the UK. In some areas there is well organised systematic
screening whilst in others there are ad hoc schemes with variation in screening
methods and population coverage, and no recording of service outcomes.8
OF DIFFERENT SCREENING METHODS
have been a number of studies assessing the effectiveness of different
screening modalities. Comparison between the studies can be difficult as
a number of different reference standards have been used, there are variations
in the definitions of retinopathy used for grading, and some studies involved
only a small number of patients and observers.
from the UK have shown sensitivity levels for the detection of sight-threatening
diabetic retinopathy of 41-67% for general practitioners, 48-82% for optometrists,
65% for an ophthalmologist, and 27-67% for diabetologists and hospital
physicians using direct ophthalmoscopy.9-13
are few studies specifically assessing the use of dilated slit-lamp indirect
ophthalmoscopy, but it does appear that the required standards may be achieved
by trained individuals. Sensitivities for the detection of referable retinopathy
by optometrists have been found to be 77-100%, with specificities of 94-100%.14
use of ophthalmoscopy has the disadvantage that there is no hard record,
which makes quality assurance more difficult. Audit of test positives or
of adverse events is not sufficient for quality assurance purposes, and
patients would need to be recalled to assess test negatives, for which
attendance rates may be very low. The personnel performing the examination
require considerable training and accreditation.
methods currently in use involve 35mm film, digital images, or polaroid
instant film prints with subsequent grading by trained individuals. The
use of mydriasis results in improved sensitivity for the detection of sight-threatening
retinopathy and fewer ungradeable images. 9,10,12 Sensitivities
for the detection of sight-threatening diabetic retinopathy of 87-100%
have been found for a variety of trained personnel reading mydriatic 45°
retinal photographs, with specificities of 83-96%.9-11 The results
were similar between different personnel performing the grading, including
trained non-medical graders. it appears that there is good agreement in
the grading of retinopathy between 35mm colour film and digital images
despite the lower resolution of the latter,15 but further evaluation of
this is needed. Sensitivities for the detection of sight-threatening retinopathy
are lower with instant polaroid photographs. Digital images have the advantage
that they are easier to acquire, store and transfer than 35mm film, and
that images can be reviewed with the patient at the time of screening.
patients also find the lower intensity flash more comfortable.
NATIONAL SCREENING COMMITTEE REVIEW OF DIABETIC RETINOPATHY SCREENING
National Screening Committee has recently considered the issues surrounding
screening for diabetic retinopathy and after wide consultation has provided
recommendations on screening and the practicalities of a national programme.
Details of these can be seen on the website: http://www.diabetic-retinopathy-screening.nhs.uk/
The National Institute for Clinical Excellent (NICE) is also reviewing
the evidence and will be producing guidelines concerning screening and
early management for diabetic retinopathy later this year.
recommendations of the National Screening Committee are:
Screening Committee assessed the cost-effectiveness of slit-lamp indirect
ophthalmoscopy, fixed and mobile digital photographic methods. A mobile
digital photographic service was found to be the most cost-effective. Although
the use of combined modalities in screening for diabetic retinopathy may
increase sensitivity levels compared to the use of ophthalmoscopy alone,
it is not clear whether this approach is more or less cost-effective. 10,16
screening for all diabetic patients aged over 123 years, or post-puberty.
imaging is the preferred modality.
assurance should be included in any programme.
ophthalmoscopy should not be used as a primary method for systematic screening
as it does not meet the required quality criteria.
slit-lamp ophthalmoscopy may meet the sensitivity and specificity requirements
but requires considerable skills and training, and it is hard to perform
adequate quality assurance.
programme should be accessible to all patients with diabetes. The exact
details of a programme for a particular area will be determined by local
national programme would be rolled out over a period of 3-4 years, as both
funding and trained staff become available.
quality assurance measures proposed in such a programme will represent
a significant workload for some ophthalmologists, and their implementation
will be the subject of further discussions.
ESTIMATIONS FOR THE PROPOSED NATIONAL SCREENING PROGRAMME
National Screening Committee has calculated the estimated costs for the
proposed national screening programme for diabetic retinopathy and has
put forward a bid to the Comprehensive Spending Review under the auspices
of the National Service Framework for diabetes. Such a programme would
require pump-priming funds of about £67 million pounds in England,
phased over several years, with 70% of the funding for a particular health
authority in the first year to allow for start-up costs. Such a programme
can be calculated to cost about £1,370 per case treated in the first
year, £12,000 per prevention of severe visual loss, and about £2,000
per sight year gained.17 By the fourth year, it is hoped that
the programme could be funded by anticipated revenue savings from a reduction
in the number of cases requiring treatment for advanced disease.
screening for diabetic retinopathy should make an important contribution
to the preservation of vision for people with diabetes and a national screening
programme has now been proposed. Its full implementation will depend on
the Diabetes National Service Framework which is expected to be published
soon. At present health authorities are being advised to take account of
the recommendations of the National Screening Committee in making decisions
on investment in equipment and staff training.
Bailey, consultant ophthalmologist, Bristol Eye Hospital.
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