Lesson 6: ART Guidelines for DR screening

Diabetes mellitus (DM) is a global epidemic with significant morbidity. Diabetic retinopathy (DR) is the specific microvascular complication of DM and affects 1 in 3 persons with DM. DR remains a leading cause of vision loss in working for adult populations.

Patients with severe levels of DR are reported to have a poorer quality of life and reduced levels of physical, emotional, and social wellbeing, and they utilize more healthcare resources.

Epidemiological studies and clinical trials have shown that optimal control of blood glucose, blood pressure, and blood lipids can reduce the risk of developing retinopathy and slow its progression.

Timely treatment with laser photocoagulation, and increasingly, the appropriate use of intraocular administration of vascular endothelial growth factor (VEGF) inhibitors can prevent visual loss in vision-threatening retinopathy, particularly diabetic macular oedema (DME). Since visual loss may not be present in the earlier stages of retinopathy, regular screening of persons with diabetes is essential to enable early intervention.

Epidemiology of diabetic retinopathy

In many countries, DR is the most frequent cause of preventable blindness in working-age adults. In the United States, an estimated 40% (8% for vision-threatening retinopathy) of persons with type 2 diabetes and 86% (42% for vision-threatening retinopathy) of persons with type 1 diabetes
have DR. High prevalence estimates have also been reported in other countries.

Despite concerns about a potential diabetes epidemic in Asia, epidemiologic data for DR in Asian countries is relatively limited. In Latin America, 40% of diabetic patients had some DR and 17% required treatment. Few studies of DR have been conducted in Africa.

DR develops with time and is associated with poor control of blood sugar, blood pressure, and blood lipids. The longer someone has had DM, and the poorer their control, the higher their risk of developing DR. Good control reduces the annual incidence of developing DR and extends life.

However, good control does not necessarily reduce the lifetime risk of developing DR, so everyone with DM is at risk.

The overall prevalence of DR in a community is also influenced by the number of people diagnosed with early DM. In resource-rich settings with good health care systems, more people with early DM will have been
diagnosed. The prevalence of DR in people with newly diagnosed DM will be low, resulting in a lower overall prevalence of DR.

In resource-poor settings with less advanced healthcare systems, fewer people with early DM will have been diagnosed. People may be diagnosed with diabetes only when symptomatic or complications have occurred. Thus, the prevalence of DR in people with newly diagnosed DM will
be high, resulting in a somewhat higher overall prevalence of DR.

In general, a meta-analysis of large scale studies show that approximately one-third of those with DM will have DR, and approximately one-third of those (or 10% of persons with DM) will have vision-threatening DR that requires treatment.

Screening guidelines

Even if an adequate number of ophthalmologists are available, using ophthalmologists or retinal subspecialists to screen every person with DM is an inefficient use of resources.

A screening exam could include a complete ophthalmic examination with refracted visual acuity and state-of-the-art retinal imaging. However, in a low-resource setting, the minimum examination components to assure appropriate referral should include a screening visual acuity exam and retinal examination adequate for DR classification. Vision should be tested prior to pupil dilation.

The screening vision exam should be completed by trained personnel in any of the following ways, depending on resources:

• Refracted visual acuity examination using a 3- or 4-metre visual acuity lane and a high contrast visual acuity chart.
• Presenting visual acuity examination using a near or distance eye chart and a pin-hole option if visual acuity is reduced.
• Presenting visual acuity examination using a 6/12 (20/40) equivalent handheld chart consisting of at least 5 standard letters or symbols and a pin-hole option if visual acuity is reduced.

A retinal examination may be accomplished in the following ways:

• Direct or indirect ophthalmoscopy or slit-lamp biomicroscopic examination of the retina.
• Retinal (fundus) photography (including any of the following: wide-field to 30 degrees; mono- or stereo-; dilated or undilated).This could be done with or without accompanying optical coherence tomography (OCT) scanning. This could also include telemedicine approaches.
• For the retinal examination, a medical degree may not be necessary, but the examiner must be well trained to perform ophthalmoscopy or retinal photography and be able to assess the severity of DR.

Minimum referral guidelines

• Visual acuity below 6/12 (20/40) or symptomatic vision complaints
• If DR can be classified according to the international classification of DR or a simplified scheme, they should be referred accordingly & (see Tables 1 and 2)
• If a retinal exam or retinal imaging is available but only a less detailed classification of DR is possible:
• – No retinopathy or only a few small red spots: return for screening exam in 1–2 years
  – Dot or blot haemorrhages or possible neovascularisation: refer to an ophthalmologist.
  – White spots in the retina: refer to an ophthalmologist.
• If visual acuity or retinal examination cannot be obtained at the screening examination: refer to an ophthalmologist
• Patients who have had laser treatment should also be referred for ophthalmic review.

Further Reading

The International Council of Ophthalmology (ICO) developed these guidelines to serve a supportive and educational role for ophthalmologists and eye care providers worldwide. They are intended to improve the quality of eye care for patients around the world. Click here to read ICO guidelines for diabetic eye care.