Extending eye screening for diabetics from every year to every two years could increase the risk of blindness, researchers said.
They also suggest that the adoption of artificial intelligence (AI) could help the NHS keep up with demand.
Eye problems – known as diabetic retinopathy – are a complication of type 1 and type 2 diabetes, caused by high blood sugars that damage the back of the eye.
Early intervention is vital to ensure vision loss does not occur.
Since 2003, diabetics aged 12 and over in England have been invited for an eye test.
In October the guidance was updated, meaning those with no signs of diabetic retinopathy for two consecutive tests will be invited back every two years, while those at higher risk will be screened more regularly.
However, a team led by researchers from Moorfields Eye Hospital said it was “unclear what clinical and other implications this change might have”.
To investigate the issue, they tracked the eye health of 82,782 people with diabetes in north-east London who were examined between 2012 and 2021 and showed no signs of diabetic eye disease at two previous examinations.
Of the cohort, 36% were white, 16% were black, and 37% were of South Asian or other ethnicities.
Over eight years they tracked the number of people who developed diabetic retinopathy, along with their ethnicity and age.
During the period, there were 1,788 new cases of sight-threatening eye disease in patients considered ‘low risk'.
Of the group, 103 people had the most severe type of the condition – proliferative or PDR – which carries a high risk of blindness and requires urgent referral.
The researchers said, based on the data, extending the annual eye exam to two years would delay diagnosis by 12 months in 56.5% of people with sight-threatening disease and 44% of PDR patients.
The analysis also showed that 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.
Blacks were 121% more likely to develop a severe form of the condition than whites.
The progression of diabetic retinopathy was also more pronounced in younger (under 45) and older (over 65) patients.
The paper, published in the British Journal of Ophthalmology, said: “The motivation for biennial screening is to free up capacity in the NHS” and “reduce inconvenience” for diabetics who are at low risk of vision loss.
According to Diabetes UK, there are around 4.3 million people in the UK with a diabetes diagnosis, but a further 850,000 people could also be undiagnosed.
The researchers also suggested that “there is a need to address the potential for increasing ethnic and age disparities in health care”, while artificial intelligence could help the health service keep pace with screening frequency.
In a linked article, Dr Parul Desai and Dr Samantha De Silva, of Moorfields Eye Hospital and Oxford Eye Hospital and University of Oxford, respectively, called for “a review and update” of the NHS diabetes screening program “to consider the differential impact between population subgroups eligible for diabetic eye screening'.
They added: “Introducing the age and ethnicity reporting requirement for selected screening patterns would allow for regular, prospective monitoring of changes in service delivery so that differences do not go unnoticed and inform responsive action on any unwarranted variation… because one size may not always fit all.”
A spokesman for the Department of Health and Social Care said: “We accepted the recommendation of the UK's National Audit Committee's independent scientific experts, which was based on a wide review of existing evidence, including 25 independent studies.
“Evidence shows that if no sign of diabetic retinopathy is detected, it is safe for people to be screened every two years. People at higher risk of vision loss will continue to see annually or more often as needed.
“This change, which has already been implemented in Wales, Scotland and Northern Ireland, will help the NHS improve the services it offers by reducing the number of appointments people with lower risk diabetes need to attend.”