Introduction: To determine the association between mean glycated haemoglobin (HbA 1c ) or glycaemic variability and the development of diabetic retinopathy (DR) in people with diabetes.Methods: An observational cohort study with people registered with a DR eye screening service between October 2012 and October 2017. Those who had no DR at the start of the study were followed for a maximum of 5 years. HbA 1c measures were used to calculate HbA 1c variability and mean HbA 1c to assess any relationship between these and the risk of developing new onset DR. Results: A total of 2511 individuals were followed up for up to 5 years. Of these, 542 (21.6%) developed DR. After adjustment, HbA 1c variability was not significantly associated with the development of DR (p = 0.3435). However, the mean HbA 1c was (p \ 0.0001). Those with type 1 diabetes had an odds of 1.63 (95% CI 1.11-2.40) of a retinopathy diagnosis compared to those with type 2 diabetes. Conclusions: We have shown that mean HbA 1c is associated with an increased risk of developing diabetic retinopathy. However, after adjustment for sex, age, diabetes type and the mean, the HbA 1c variability no longer remained significant. Our data suggest that optimizing long-term glycaemic control remains paramount.