Extending diabetic eye screen to 2 years could risk critical treatment delays and sight loss

Extending annual screens by one year for people considered to be at low risk of diabetic eye disease (diabetic retinopathy) in England could lead to serious delays in treatment and/or risk of vision loss, suggests a large, real-world data study published online. British Journal of Ophthalmology.

Researchers say early treatment is essential to prevent blindness. The 2-yearly screen delayed hospital referral by 12 months in nearly half of those with severe diabetic eye disease, with those at both ends of the age spectrum and black ethnicity most at risk, the findings indicate.

A review and update of diabetic eye screening program standards and their reporting requirements has now been completed, and concludes in a linked editorial.

The NHS introduced an eye screen (DESP) for people with type 1 or 2 diabetes from the age of 12 in England in 2003, with the aim of picking up diabetic eye disease – damage to the delicate network of small blood vessels in the back. Eye – for which early treatment is essential to stop vision loss.

Since 2016, the UK National Screening Committee has recommended annual eye examinations for those at high risk of vision loss and 2-yearly checks for those considered at low risk, in light of evidence that this interval is safe and cost-effective. Amid growing demand for services, explain researchers.

Already elsewhere in the UK, it is now being implemented in England. But what the clinical and other implications of these changes might be is unclear, the researchers say. To plug this knowledge gap, they drew on the largest screening in North East London, one of the most ethnically diverse diabetic programmes.

They tracked the eye health of 82,782 people with diabetes who had two consecutive screens between 2012 and 2021 but no diabetic eye disease. 16% were black.

Over 8 years, they looked at the number of people who developed the condition, their ethnicity and age, as well as the effects of a possible delay in referral for treatment as a 2-year outcome rather than an annual eye exam.

During this period, 1,788 new cases of moderate to severe (sight-threatening) diabetic eye disease were found in people considered to be at low risk: 103 of these were the proliferative form (PDR) – the most severe type associated with end-stage diabetes. Damage that carries a very high and short-term risk of blindness and requires urgent referral.

Men had lower rates of sight-threatening diabetic eye disease than women, and those with type 1 diabetes had higher rates than those with type 2 diabetes. There was no clear pattern across levels of deprivation.

But racial differences emerged over time. The case rate was significantly higher among blacks, who were 121% more likely to develop sight-threatening diabetic eye disease than whites, while South Asians were 54% more likely.

Based on these statistics, extending the annual eye examination by 2 years would delay diagnosis by 12 months in more than half (1007; 56.5%) of those with vision-threatening disease and in almost half (44%; 45). PDR.

Diagnostic delays stratified by ethnic group were 256/30,350 among whites, 379/29,730 among South Asians, and 256/13,391 among blacks—equivalent to 844, 1276, and 1904 per 100,000 groups, respectively.

For PDR, the number was much lower, but the rate was still higher among black people (90/100,000) than among whites (46/100,000).

Progression of sight-threatening eye disease was also more pronounced among the youngest (<45 years) and oldest (65+) than among those in their mid-40s-60s.

Diagnostic delays stratified by age were greatest among those under 45 (1504 per 100,000 screened) and 65 and older (1248) compared with 1178/100,000 among 45- to 54-year-olds and 987 among 55- to 64-year-olds.

The researchers acknowledge several limitations of their findings, including the use of annual screening data to simulate 2-yearly screening.

But they wrote: “Given these sociodemographic differences, we have shown that introducing biennial as opposed to annual diabetic eye screening may worsen vision loss in some sociodemographic groups because of delayed detection. [sight threatening diabetic retinopathy] and PDR, potentially adding to health care disparities.”

And they stress: “The impetus for biennial screening is to free up capacity and reduce hardship in the NHS. [people with diabetes] Attending an eye screening appointment each year lowers the risk of vision loss, but there is a need to address the potential for exacerbating racial and age disparities in health care.”

They suggest that “artificial intelligence (AI) technologies can be used to help maintain current status on screening frequency”. But despite their well-proven effectiveness in reducing the human workload of grading retinal images for diabetic eye disease, automated systems, which have been used in Scotland for over a decade, are not currently licensed for use in English NHS DESPs.

In an accompanying editorial, Dr Parul Desai and Samantha de Silva, respectively, Moorfields Eye Hospital London and Oxford Eye Hospital and University of Oxford, comment: “Given the significant changes in service delivery that have either already occurred or are imminent, and the evidence now available, DESP standards And a review and update of their reporting requirements (most recently done in 2019), should be planned to consider the differential impact among population subgroups eligible for diabetic eye screens.”

They add: “Introducing a requirement to report screening by age and ethnicity to selected standards will enable regular, prospective monitoring of changes in service delivery, so that disparities do not go unrecognized, and provide information for responsive action to any unwarranted changes… because a One size may not always fit all.”