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Diabetic Retinopathy Screening Services in Scotland: Recommendations for Implementation



Diabetic Retinopathy Screening: Overview of the Screening Process

11. The HTBS report set out the objectives of the Scottish screening programme as:

  • Primary objective. The detection of referable (potentially sight-threatening) retinopathy so that it can be treated.

  • Secondary objective. The detection of lesser degrees of diabetic retinopathy. This can have implications for the medical management of people with diabetes in terms of blood pressure and glycaemic control, important risk factors for STDR (sight threatening diabetic retinopathy).

12. The basic process of retinopathy screening can be simply described and Figure 1 below outlines the main stages. The difficulty arises in operating the system to a high standard consistently over a long period of time, whilst at the same time maintaining fail-safe procedures to ensure that all appropriate patients are offered regular screening and are referred for appropriate treatment when they need it.

13. One of the most important elements of operating DRS is the rule set which determines how patients flow through the system. Such rules, for example, define exclusion criteria and set out how patients who did not attend (DNA) or could not attend (CNA) should be handled. It is essential to ensure that patients do not inadvertently drop out of the routine annual invitation to screening e.g. by moving NHS Board of residence, moving GP practice, or changing name or address; by error, accident, mis-keying details or unauthorised clinical decision. Drawing upon the experience of existing DRS schemes and upon the lessons learned in the operation of other national screening programmes, the national rule set for DRS is currently being developed and will be published in the DRS Manual.

Key statement 5: To ensure consistency, local provision of DRS must follow the nationally agreed rule set. The rule set will be published in the DRS Manual. No individual Board will be permitted to define its own rules.

Figure 1: Overview of the diabetic retinopathy screening process


14. It is essential to develop software to enable the screening process to operate efficiently and consistently. Further details of how and when the software to support DRS will be developed are outlined below ( see paragraph 52).

Diabetic Retinopathy Screening: Patients and the Public

Patient Expectations

15. The public may have an unrealistic view, encouraged by legal judgements, that screening is expected to guarantee prevention of disease, or in this case, its complications. Any diabetic retinopathy screening programme must therefore ensure the public have a realistic expectation of what the programme is designed to achieve.

16. Given that the service to be introduced is designed to reduce the risk of retinopathy, the DRSIG considered whether to recommend that the programme be called a 'risk reduction programme' rather than a 'screening programme'. However, it was concluded that because 'screening' was such a familiar term it should continue to be used but that it should be emphasised that diabetic retinopathy screening did not and could not offer any guarantee that a patient would never suffer loss of vision.

17. All literature must state clearly what the diabetic screening programme cannot provide. NHS Boards must inform patients that the identification of co-existing eye disease is not a function of the diabetic retinopathy screening programme.

18. There is convincing evidence that the identification of diabetic retinopathy at the appropriate stage will reduce the risk of serious loss of vision in most cases if modern treatment is applied. However, the threat of serious loss of vision remains even with effective screening for the following reasons:

  • Not all cases of retinopathy will be detectable even with digital photography.

  • Accelerated forms of diabetic retinopathy can develop between screening intervals.

  • Even with effective treatment performed to the highest standards, some patients will not respond.

Key statement 6: NHS Boards must clearly articulate what the screening programme is designed to achieve and the public must be made aware of its limitations.

Key statement 7: Diabetic retinopathy screening will not remove the need for regular general eye examination by optometrists to monitor changes in refraction and to detect other eye disease.

Measuring Success

19. Although technical efficiency and clinical effectiveness are important, the DRS programme must also meet the needs of patients. The screening process should be characterised by partnership, dialogue, negotiation and choice. Patient satisfaction with the DRS service must be monitored alongside the clinical aspects of the programme.

Key statement 8: Patient perceptions and the promotion of confidence, together with patient information, involvement and empowerment, equity of access and emotional and practical support will be crucial to the successful implementation of DRS. To ensure these important issues are incorporated in the programme, service uptake and patient satisfaction will be monitored. A patient information leaflet to be used nationally will be provided in the DRS Manual for NHS Boards.

Emotional and Practical Support

20. Patients need time and support to make sense of the medical information they receive, especially where such information may imply significant change in their lives. There should be a named contact person with whom to discuss screening outcomes or treatment options. Patients will want to choose when, where, and from whom to receive emotional support; in addition to nursing, nurse counselling, medical and social work staff, eye clinic liaison officers (where appointed) can fulfil this task. Voluntary organisations working in the fields of diabetes and visual impairment also offer emotional help and support, and may host user-led self-help groups. Where it comes to the attention of screening staff that a patient is experiencing practical difficulty arising from the effects of diabetes in general, or of diabetic retinopathy in particular, referral to a social work agency should be discussed. Patients who develop problems with their sight and require low vision aids or rehabilitation assessment should be referred promptly to the appropriate services.

Key statement 9: NHS Boards should ensure that information about low vision and rehabilitation services is readily available.

Patient Representation

21. Patients, carers and their representatives should be involved in the development of diabetes services and in the implementation and monitoring of the DRS programme. NHS Boards should consider how best to achieve this in the context of local circumstances. At a national level, patients should be represented on the DRS collaborative network ( see paragraph 85).

Key statement 10: Patients should be represented on the executive group of the DRS collaborative network ( see key statement 39). In addition, a sub group should be set up to monitor the views of patients and ensure that the DRS programme meets their needs.

Consent to Screening

22. The report of the Confidentiality and Security Advisory Group for Scotland (CSAGS) - Protecting Patient Confidentiality, Final Report (11) - states that implied consent for multiple uses of healthcare data, as in the case of disease registers, is acceptable. It is expected that the developing regional diabetes registers will provide the diabetic retinopathy screening programmes with the patient data (diagnosis and demographics) to allow those patients to be called for screening. Once the patient has been invited to attend for screening the use of the patient identifiable data then comes under the category of direct patent care. Patients must be informed about the uses to which their data may be put but consent can be assumed.

Key statement 11: The diabetic retinopathy screening programme is a form of direct patient care. Informed but implied consent to screening is therefore applicable.

23. NHS Boards must have clear mechanisms for identifying and acting on refusals by following the principles set out in the CSAGS report. NHS Boards must also ensure patients are made aware of the implications for themselves should they decline the offer of being screened.

Diabetic Retinopathy Screening: Local Developments

24. The progress being made by NHS Boards to provide retinopathy screening to all people with diabetes in their area was surveyed during the second half of 2002. A summary of the findings can be found at Annex H. A number of areas have already made significant progress. The DRS programme in Grampian follows the specifications of the HTBS report very closely and has provided valuable experience on which to base the recommendations in this report. The developing programme in Glasgow also offers helpful insights into how best to establish a new DRS service.

Key statement 12: All NHS Boards in Scotland are taking steps to develop diabetic retinopathy screening programmes but none is so far advanced that the proposals in this report will inhibit local development and implementation.

Diabetic Retinopathy Screening: Staffing

Key statement 13: Conventional professional boundaries should not be allowed to constrain staffing structures for the screening programme. For example, retinal screeners and graders may be nurses, optometrists, orthoptists, medical photographers or others who may not have experience in healthcare but who receive appropriate training, accreditation and monitoring.

Camera Operator/Retinal Screener

25. The camera operator will be responsible for taking retinal photographs and ensuring they are of adequate quality. Camera operators will also be responsible for downloading digital images to a central database, which would ideally be linked to the regional diabetes register. If the camera is housed in a mobile unit, then the camera operator will also drive the van. Camera operators may also be trained as graders but as a minimum requirement they must be able to recognise an unsatisfactory image so that appropriate action (by following the 3 stage protocol) may be taken to allow mydriatic photography to be performed at the same visit.

Instillation of Eye Drops

26. The three-stage screening process for diabetic retinopathy recommended for use in Scotland will require the instillation of eye drops for mydriasis (pupil dilation) in a minority of cases when required to obtain a satisfactory image. At present, doctors and optometrists are allowed to instil eye drops and for the purpose of mydriasis under a Patient Group Direction (PGD) nurses may also apply drops. Other groups of personnel who may act as screeners may be able to fulfil the requirements of a PGD if changes are made to the regulations. NHS Quality Improvement Scotland and the National Screening Committee are seeking changes to the UK regulations.

Key statement 14: There is an urgent requirement to include retinal photographers in the patient group direction on the use of eye drops for mydriasis.

27. In the meantime, local arrangements may be made to avoid undue restriction to screening work. For example, as retinal screening will take place in a variety of locations such as hospital clinics or GP practices there may be other staff available to install eye drops. A medical photographer in a hospital clinic may therefore have access to a nurse who could administer the eye drops if necessary.


28. A three-level system for grading digital retinal images is recommended. This multi-level approach should reduce the number of unnecessary referrals to ophthalmology. Level 1 graders will grade images for image quality and the presence or absence of diabetic retinopathy. Images with any retinopathy (whatever level) will be passed on to the level 2 grader. Any individual undertaking this should have undergone a recognised and accredited training programme. In due course it is hoped this role will be performed by automated grading systems. Level 2 grading will involve an examination of all remaining pictures. It is anticipated that this will be between 20% and 30% of the total. These Graders will be required to undergo a more intensive training programme which has been recognised and accredited. The purpose of level 2 grading is to identify sight threatening retinopathy and other retinal problems that may be amenable to treatment. Such images will be passed on to the level 3 grader for a final assessment to be made. The role of level 3 graders (who usually but not necessarily will be ophthalmologists) is to confirm or refute the need for referral to ophthalmology. Patients stay within the screening programme until referral by a level 3 grader to ophthalmology. Level 1 and level 2 grading could in some circumstances be performed by camera operators who have received sufficient training. This would give a greater variety to the post and make it more interesting and sustainable for the long term.


29. An administrator is required in each area providing a DRS service to organise the call and recall system and to run it. They would also be responsible for audit data and quality assurance checks on both the Camera Operators and the Graders. Such administrators may not necessarily need to perform the quality assurance themselves but would need to organise it. They would, however, be involved in performing the audits. The Administrator would have responsibility for ensuring that the results of the graded images are returned to the GPs, Diabetes Clinics and Ophthalmologists where relevant and ensure that the results and preferably the images themselves are linked into the Regional Diabetes Register. The administrators would also arrange training for new Camera Operators and Graders. They may require secretarial support. Specialist IT support would be needed to maintain links between the Regional Diabetes Register and the screening programme (e.g. obtaining the demographic data from the Regional Register which will feed the call/recall system; transferring the digital images and reports back into the Regional Register).

Quality Assurance

30. A suitably qualified and trained individual will be needed to undertake quality assurance on the quality of the photographs and the grading results. Each grader will need to have a proportion of their photographs audited annually. The quality assurer may be the administrator or ophthalmologist or other suitably trained individual. External quality assurance will be performed by the DRS Network Co-ordinator. More detail about quality assurance issues is included below ( see paragraph 65).

Strategic Management Issues

31. Although the Administrator will be in charge of day to day running of the Retinal Screening Programme there needs to be a lead clinician in overall charge of strategic issues with regard to retinal screening and its interface with Primary Care, Diabetes Registers and Hospital Diabetes Clinics. This individual would also be expected to take responsibility for making decisions about new technological developments and for the policy for patients who do not attend. This may be a Public Health Physician or some other relevant individual. The lead clinician would be expected to participate in the DRS collaborative network described below ( see paragraph 85).

32. To create efficiency, smaller NHS Boards should work together to provide the screening service for their population. Grading could also be centralised or retained locally. Centralising and sharing services has considerable cost benefits ( see paragraph 103) but may also have significant organisational benefits. Cross-boundary schemes will require careful implementation.

Optometrist Involvement in the National Screening Programme

33. Optometrists have an important role to play in the national screening programme. They could contribute to the screening programme in a number of ways which can be adapted and developed to suit local needs:

(a) Within the community, as an interim measure, to maintain an existing scheme using slit lamp biomicroscopy, while digital cameras are being introduced.
(b) Within the community as part of a new scheme in which digital cameras will be sited in optometry practices.
(c) Within the community providing a service using digital cameras sited in GP practices or community hospitals.
(d) Within hospitals as either hospital optometrists or sessional community optometrists using digital cameras.
(e) As primary or secondary graders.
(f) By providing slit lamp biomicroscopy examination where digital photography has failed to provide a satisfactory image. This could be performed in the local community practices or in central locations.

34. Existing schemes utilising optometrists and slit lamps will need to be modified by evolution and agreement locally to meet the requirements outlined in this report, in particular the need to align existing arrangements for training, accreditation and quality assurance with the NHS Quality Improvement Scotland proposals. In addition, the move to digital photography will need to be made to meet the deadline for the implementation of a fully digital screening service by March 2006. IT, call/recall, registers and grading will also have to be introduced to meet the requirements of the national scheme. It may be desirable for those optometrists involved in the programme to be linked to NHSnet. It will be vital not to lose the support of those participating in existing schemes during the transitional phase.

35. New community schemes involving optometrists will ideally use digital photography at the outset. However, NHS Boards could consider using slit lamp biomicroscopy if that enabled a scheme to be introduced quickly where otherwise (perhaps because of funding constraints) a rapid introduction of a digital programme would not be feasible. A precise timetable for moving to digital cameras must be specified. Training, assessment, and accreditation will need to be in line with national guidelines recognising that because of their professional qualifications the additional training requirements for optometrists will differ from other providers.

36. Indicative fees for optometrists are dealt with in the section on funding requirements ( see paragraph 107). Costing for optometrists will depend on the optometrist's role ( see paragraph 33).

37. It is likely that some digital cameras will be sited centrally within hospitals. Hospital optometrists, where available, may be able to act as primary or secondary screeners or graders. Their particular skills could also be utilised for training other staff and to reduce the additional burdens on ophthalmology. Community optometrists with a special interest in diabetes may also be prepared to act in this capacity on a sessional basis. Experienced optometrists might also undertake level 3 grading with agreement of ophthalmologists and after appropriate training.

38. In the unusual circumstance of a domiciliary examination being required the normal arrangements for domiciliary optometric examinations should apply.

Diabetic Retinopathy Screening: Training

39. All those involved in providing DRS services should be receiving a quality assured programme of continuing professional development in line with specified minimum continuing training requirements as well as being subject to regular appraisals, assessments and reaccredidation. Continuing education will be required to prepare for changes in the service which will occur as the DRS programme evolves.

40. Retinal screeners and graders will require specific training, accreditation and regular performance assessment. Topics to be covered include:

  • Clinical knowledge and skills

  • Imaging and IT skills

  • Operational issues

  • Grading.

41. A Training Steering Group has been established in Scotland and this group has produced a training manual and developed a training curriculum that is in the pilot stage. To date, two courses have been run, the first in Grampian, and the second in Tayside. NHS Education has been asked to accredit the training curriculum and training materials. In order to ensure that appropriate training is available and accessible for the whole of Scotland, NSD should liaise with users to assess training requirements and commission appropriate training centrally on behalf of NHSScotland. Training should be delivered as locally as possible to enable the photographers to be trained on equipment relevant to them. In addition, local training will allow the local ophthalmologist (who is also likely to be the level 3 grader) to deliver the training on grading and so develop confidence in the graders' ability.

Key statement 15: Training and accreditation in diabetic retinopathy screening must be carried out to the appropriate quality standard. NHS Education should be responsible for the accreditation of training. NSD should be responsible for commissioning an appropriate, locally delivered training scheme.

Key statement 16: A training handbook for screeners and graders will be published by June 2003.

42. Ideally, staff should be trained to standards that are uniform throughout the UK. To this end the training handbook and curriculum developed in Scotland by the Training Steering Group are being considered for adoption throughout the United Kingdom.

Diabetic Retinopathy Screening: Grading

43. The grading scheme recommended by HTBS has been reviewed and amended in the light of concerns about its complexity and in order to bring it into line with the emerging UK scheme. The revised scheme - the Scottish Diabetic Retinopathy Grading Scheme 2003 - is included in Annex E.

Key statement 17: The Scottish Diabetic Retinopathy Grading Scheme 2003 should be assessed for effectiveness and efficiency and reconsidered as appropriate in the light of new developments in the UK and abroad.

44. The Scottish Diabetic Retinopathy Grading Scheme 2003 can be used manually and NHS Boards are encouraged to adopt it as soon as possible. However, to be used most efficiently, a grading scheme based on observable features depends upon software. Grading software must be integrated with call/recall software. Ideally grading and call/recall would be combined in the same software package but as a more realistic option two systems could be integrated. The decision is largely a technical one and will be made as soon as possible. In any event, grading software should be procured centrally. The full advantages of the Scottish Diabetic Retinopathy Grading Scheme 2003 will not be achieved without appropriate software.

Key statement 18: The Scottish Diabetic Retinopathy Grading Scheme 2003 can be used manually and NHS Boards are encouraged to adopt it as soon as possible. However, until a national grading software programme has been procured, use of the Scottish Diabetic Retinopathy Grading Scheme 2003 should be at the discretion of each individual Board.

Diabetic Retinopathy Screening: Cameras and Image Transmission

45. A national screening programme for diabetic retinopathy implies a standardised screening technology. However, the operational difficulties of implementation must be recognised and consequently a pragmatic approach will be necessary as the programme develops. It is therefore important to provide practical guidance for NHS Boards to develop their own service, making best use of existing technology with recommendations for improvement.

Key statement 19: Digital technology for cameras and image transmission has provided the opportunity for a national screening programme to be introduced at a reasonable cost. It provides permanent and accessible clinical photographs for quality monitoring and review.

46. The technology is developing rapidly and there is now a bewildering choice of cameras and interfaces. The following topics need careful consideration:

  • Camera interface

  • Camera resolution

  • Storage of images

  • Image transmission and bandwidth requirements

  • Image compression ('lossy' vs 'lossless')

  • Screen resolution and display technology

47. In view of the rapidly changing technology, guidance about which cameras to use needs to evolve as change and circumstance dictate. A Four Nations Working Group set up by the National Screening Committee has been working in consultation with the manufacturing and software industry to produce a recommended specification for cameras. A specification was published in February 2003 and can be found on he NSC website A National Screening Programme for Sight-Threatening Diabetic Retinopathy < www.nscretinopathy.org.uk>. The intention is to regularly update these recommendations.

Key statement 20: Digital technology will continue to advance but the specification required to support diabetic retinopathy screening may now be defined. To this end, the DRSIG will continue to contribute to UK wide discussions to agree the appropriate specification in conjunction with camera manufacturers.

Camera Choice

48. A useful minimum camera resolution is necessary to underpin effective screening and it should be noted that many sites have been effectively using cameras with resolutions of around 800 x 600 pixels for several years. The HTBS report cites the UK National Screening Committee (NSC) recommendation of 20 pixels/degree - a resolution of 1365 x 1000 minimum resolution. Existing cameras should continue to be used but with a plan to meet the new minimum resolution standard (1365 x 1000) as time and circumstance permit. Available cameras with a resolution of 1360 x 1024 pixels meet this requirement. All new camera procurement must match this minimum standard. In ascertaining compliance with the minimum standard allowance must be made for the size of black image masks and the reduction in effective resolution inherent in single chip cameras.

Image Size

49. Increased image size is likely to become available as technology advances. It is, however, important to note that effective grading is not simply a function of image size or resolution. Extremely large images are impractical because the image may need to be reduced to avoid excessive scrolling. Where any form of image reduction has been employed, the reduction/compression mechanism must be evaluated and accredited to ensure screening sensitivity is not affected by the reduction. Evidence gained through a formal controlled trial would provide sufficient evidence for accreditation. Experience of such trials in Tayside is available. Any method employed must not be capable of being altered by the user and if a compressed image standard has passed scrutiny, no deviation from this standard can be permitted. Lossless compression should be employed where possible.

Key statement 21: Because technical developments have occurred so rapidly there is limited evidence to help formulate the minimum camera specification or to assess the utility of different options for image compression. Research is required to determine the optimum pixel resolution required for adequate screening. These issues should be kept under review by the DRS collaborative network; ( see key statement 39).

Display Technology

50. Recommendations on display technology all conclude that images should be viewed 1:1 or pixel for pixel during grading. In addition, excessive scrolling should be avoided by the use of monitors of a resolution appropriate to the resolution of the image utilised. 60% of the image must be viewable on the screen, vertically and horizontally, at any one time. As stated earlier, this may imply the reduction of very high-resolution images prior to screening. Screen size is dictated by the resolution of images to be graded and the resolution of the display necessary to avoid excessive scrolling. CRT (Cathode Ray Tube) monitors are preferable to TFT (Thin Film Transistor) flat screen displays because of the larger contrast range available on CRT monitors. Calibration and the quality assurance of monitors used for retinal grading is possible using photopic luminance calibration. This is under investigation and may permit the future recommendation of TFT flat screen monitors.

Siting of Cameras

51. In addition to technical considerations, there will be a need for individual areas to determine the appropriate configuration of cameras to suit local geography and methods of working. The screening software must be sufficiently flexible to cope with the different ways in which image capture may be managed. This may include a mix of static cameras in hospitals, mobile units and community based cameras. An important operational consideration will be integrating the annual review process at diabetes clinics and the DRS programme. Where hospitals have static cameras it might be more convenient for patients to have their eyes screened as part of the annual review, rather than being called for a second appointment for retinopathy screening. The screening process must be able to ensure not only that all appropriate patients are invited for screening, but also that patients are not recalled unnecessarily. The importance of effective software to manage these potentially complex patient flows cannot be underestimated.