Diabetic retinopathy is the main cause of blindness in adults in the UK
About 130,000 people with diabetes in London are at risk of losing their sight because of inadequate screening, according to health campaigners.
A third of diabetes sufferers in the city are not being screened for diabetic retinopathy, said Diabetes UK.
The condition is the primary cause of blindness in the UK's working-age population, the charity said.
It wants free annual retinal screening for everyone aged 12 and over who sufferes from diabetes.
"If retinopathy is caught early and treated properly then blindness can be prevented in 90% of cases, so the simple screening process really could save the sight of hundreds of thousands of people," Roz Rosenblatt from Diabetes UK said."
Latest government figures show that 130,699 people with diabetes aged 12 and over in London did not receive digital retinal screening in the year ending March 31 2008.
The national average for people that did receive screening was 67.7 per cent%, but this figure was 64.4% in London, the charity said.