Improving the uptake of screening for diabetic retinopathy

Diabetes and its myriad complications are a major public health issue.1 The prevalence of diabetes has doubled in the past 20 years to around 5.1%–7.4% of the Australian population, largely as a result of the ageing population, increasing obesity and lifestyle changes.2,3 It is estimated that the number of people worldwide with diabetes will double to 300 million by 2025.4

In 1995, the cost of diabetes to the Australian community was estimated to be at least $1 billion.1 The major cost arises from treatment of the various complications of the disease, some of which can be mitigated with better control of blood glucose, blood pressure and cholesterol levels, and with earlier detection through screening.

Diabetic retinopathy is a major cause of blindness in working-age adults in developed countries, but effective treatments are available,5 so early detection is important. Of those diagnosed with diabetes, 10% will have retinopathy at the time of diagnosis, and the rest will develop some retinopathy over the next 20 years.6 In Australia, the prevalence of retinopathy among those with diabetes is around 25%–35%,7 but only 23%–50% of those with diabetes had seen an ophthalmologist within the previous 2 years,8,9 the minimum period recommended by the National Health and Medical Research Council.10

We previously found that 74% of general practitioners did not routinely examine the eyes of their diabetic patients, instead referring to an ophthalmologist for assessment.11 Time constraints and lack of confidence in detecting retinal signs were the two biggest barriers to increased screening by GPs. Although lack of confidence could be overcome with skills transfer workshops, the lack of time is a more difficult obstacle. The current Medicare reimbursements are a disincentive for GPs to conduct diabetic retinopathy screenings. Team Care Arrangements, which require co-management with two other health professionals, encourage GPs to engage someone else to perform screenings.

In this issue of the Journal, two studies describe screening for diabetic retinopathy using fundus photography. In one study, professionals perform the screening, while in the other, screenings are conducted by trained staff.

Larizza and colleagues describe opportunistic screening, with staff at a pathology collection centre taking fundus photographs.12 This is an attractive model, but apart from the limited proportion of gradable photos, the main problem was poor follow-up of patients needing further specialist assessment. Robust and effective communication between screening services and GPs about the need for ophthalmology assessment is critical whenever clinical care is “outsourced” without initiation by the GP. This creates a potential medicolegal issue. An alternative may be a centralised system to monitor screening compliance and outcomes with appropriate recall and follow-up, such as in the United Kingdom.13 A better approach would be for the GP to take responsibility for ordering the screening test and following up the result for the individual patient, as is done for other tests. This approach would also be better for dealing with ungradable photos or a poor visual acuity result, as there is a clear clinical responsibility.

Screening in non-urban areas has particular challenges and requires adaptation of the model, but the process is still best directed by the GP. Ku and colleagues found that an undilated fundus photo provided an 83% discriminant ability for detecting any diabetic retinopathy, which may be reasonable for screening purposes.14 However, even with “professional” photography, 11% of the photos were ungradable — dilation does make a difference. A false negative rate of 26% for detecting any diabetic retinopathy may also induce a degree of complacency, and is a missed opportunity for better diabetic care. The 14% false negative result for vision-threatening diabetic retinopathy would come at a significant cost if this was the only method of screening. Photo screening in remote communities would complement existing visiting ophthalmology services by identifying those patients in need of specialist assessment beforehand. This would hopefully reduce the chance of missed opportunity and improve patient outcomes.

The increasing prevalence of chronic diseases such as diabetes requires paradigm shifts in models of health care delivery, compared with models of care for acute conditions. The aim of screening is to prevent complications and so deliver improvement in quality of life. This ultimately reduces the financial burden on the community. Many GPs find the direct ophthalmoscope challenging to use, but they do understand the implications of the clinical findings. Newer, cheaper handheld devices (such as iPhone adapters or other specific cameras) would better empower the primary care practitioner and streamline the referral process. Dilating the patient’s pupils is safe, and will always be beneficial. Notwithstanding the benefits of current retinopathy screening techniques, which require less technical proficiency, the challenge is finding the best means of delivering these services to the community.