The first guideline on type 2 diabetes from NICE aims to reduce sight loss due to retinopathy by early detection and effective treatment, explains Professor Richard Baker

Type 2 diabetes is becoming more common, and more than 60% of those affected will have diabetic retinopathy within 20 years of its onset. In industrialised countries, diabetic retinopathy is the leading cause of blindness in people under 60 years of age. Yet the risk of visual impairment and blindness is reduced by early detection and effective treatment.

The National Institute for Clinical Excellence (NICE) has just released a national guideline on the screening and early management of retinopathy in people with type 2 diabetes,1 and all primary healthcare teams involved in caring for people with diabetes should take note of its recommendations.

Origin of the guideline

The guidelines were initially commissioned in 1999 by the Department of Health. Their development has been led throughout by Professor Allen Hutchinson of the School of Health and Related Research at the University of Sheffield on behalf of a collaboration between the Royal Colleges of General Practitioners, Physicians and Nursing, and Diabetes UK. The programme for development of national guidelines has been handed over to NICE, and these guidelines have now been published by the Institute for use in the NHS in England and Wales.

The guidelines are based on the best available evidence. Extensive literature reviews were undertaken to identify evidence, and the reviews were submitted to a panel that included two diabetologists, an ophthalmologist, an optometrist, a public health physician, two GPs and an advisor from Diabetes UK.

The recommendations of the guideline panel are intended for clinical staff in primary and secondary care actively involved in the management of people with type 2 diabetes, and responsible for the initial detection and appropriate referral of those with retinopathy.

In common with other NICE guidelines, the levels of evidence are graded from Ia to IV and the recommendations from A to D, according to the strength of the underlying evidence (see Tables 1 and 2 below).

Table 1: Levels of evidence*
*Reproduced from management of type 2 diabetes, retinopathy - screening and early management. NICE Inherited Clinical Guideline F, by kind permission of the National Institute for Clinical Excellence
Table 2: Grading of evidence2*
*Reproduced from management of type 2 diabetes, retinopathy - screening and early management. NICE Inherited Clinical Guideline F, by kind permission of the National Institute for Clinical Excellence

The recommendations

Regular care

The routine management of diabetes has a critical role to play in preventing complications, including retinopathy. The guideline recommends maintenance of blood pressure at or below 140/80mmHg, and good blood glucose levels, preferably HbA1c <6.5-7.5% (grade A recommendation).

There is good randomised control trial evidence that attention to these basics of diabetes management reduces the risk of development of diabetic retinopathy.

Routine testing

The guideline recommends that the eyes of people with type 2 diabetes should be examined at the time of diagnosis and at least annually thereafter, including those registered blind and partially sighted. This recommendation was graded B.

The examination should include a check of visual acuity, corrected with glasses or pinhole. If the patient has cataracts that interfere with vision or the retina is otherwise obscured, the patient should be referred for a specialist opinion.

Depending upon the results of the examination, eye care can then be classified as routine care, early review required or referral required.

Routine care consists of annual review, and applies to people who have no retinopathy present, or only minimal or mild background retinopathy.

Early review is classified as examinations every 3-6 months, and includes patients in whom lesions have worsened since the last examination, those with scattered exudates more than one disc diameter from the fovea, and those at high risk of progression, e.g. because of a rapid improvement in blood glucose control or the presence of hypertension or renal disease.

Referral required: see Table 3 (below) for recommendations.

Table 3: Recommendations for referral
Note: The guideline recommends that local definitions of 'urgent' and 'soon' should be agreed, suggesting that a maximum wait of 1 week would be appropriate for the urgent category, and 4 weeks for the soon category

Testing methods

The guideline development panel recommended the use of tests shown to achieve a sensitivity of 80% or higher, a specificity of 95% or higher and a technical failure rate of 5% or lower.

Retinal photography was regarded as the most practical method at the present time, but slit-lamp indirect ophthalmoscopy can also be effective in trained hands. Mydriasis is required before examination unless contraindicated.

The recommendations about which tests to use are important. The available literature does not establish firm rules about who should or should not perform a test or which method to use. There were examples of individuals from different disciplines who could achieve satisfactory levels of performance. On balance, however, retinal photography was more likely to be associated with achievement of the standard set in the recommendations. Direct ophthalmoscopy was less likely to be satisfactory.

Thus, if primary healthcare teams are still reliant on direct ophthalmoscopy, they should be sure that in performing this examination they can achieve the level of sensitivity and specificity recommended in the guideline. If not, they should be requesting the provision of an alternative testing service.

The guideline also makes it clear that opportunistic screening is not a satisfactory alternative to participation in a formal screening programme. Primary healthcare teams should therefore ensure that people with diabetes are enrolled in a systematic screening programme.

The guideline includes a simple algorithm, and this may be helpful in local planning (see Figure 1, below).

Figure 1: Algorithm for the early management of diabetic retinopathy in type 2 diabetes
*Reproduced from management of type 2 diabetes, retinopathy - screening and early management. NICE Inherited Clinical Guideline F, by kind permission of the National Institute for Clinical Excellence

Implications for teams

Many practice teams will have already established systematic screening schemes, or have arrangements for ensuring that their patients are enrolled in schemes. The guideline should encourage all teams to review their schemes, and make changes if necessary.

The provision of information about eye care to people with diabetes is likely to be important in ensuring that eye examinations are undertaken regularly.

Practice teams are also encouraged to consider audit to monitor implementation of the guideline, and several criteria are suggested.

It may be helpful to place audit of the scheme for diabetic retinopathy in the context of primary care of diabetes in general. Reference to related guidelines would therefore be appropriate. These include another guideline in this series from NICE on renal disease (prevention and early management) in type 2 diabetes3 (see NICE guideline aims to reduce early diabetic renal disease) and a guideline on foot care in type 2 diabetes published 2 years ago.4

Primary healthcare teams should already have received a copy of the guideline. If not, they can obtain one from the NHS Response Line by phoning 0870 1555 455 and quoting reference no. N0058. The guideline also includes a patient and carer information leaflet, Screening for and early management of eye problems (diabetic retinopathy), which can be obtained by quoting reference no. N0059 for an English version and N0060 for an English/Welsh version. The full version of both guidelines can also be downloaded from the NICE website (www.nice.org.uk).

References

  1. National Institute for Clinical Excellence (2002) Management of type 2 diabetes, retinopathy -screening and early management. NICE Inherited Clinical Guideline E. London: National Institute for Clinical Excellence. Available from www.nice.org.uk
  2. Eccles M, Freemantle N, Mason J. North of England Evidence Based Guideline Development Project: guideline for angiotensin converting enzyme inhibitors in primary care management of adults with symptomatic heart failure. Br Med J 1998; 316:1369-75.
  3. National Institute for Clinical Excellence (2002) Management of type 2 diabetes, renal disease -prevention and early management. NICE Clinical Guideline F. London: National Institute for Clinical Excellence. Available from www.nice.org.uk
  4. Gadsby R. National guideline on diabetic foot care aims to reduce amputations. Guidelines in Practice. May 2000; 3: 27-36