Aims: Retinopathy is considered the complication most closely associated with and characteristic of diabetes mellitus. Hyperglycaemia below levels diagnostic of diabetes, so called pre-diabetes, is associated with a low prevalence of 'diabetic' retinopathy. However, few longitudinal studies of non-diabetic populations have performed repeated measures of glycaemia and screened for retinopathy to determine its occurrence in the non-diabetic population and the onset of retinopathy in new-onset diabetic patients. We determined the prevalence of retinopathy characteristically seen in diabetes in persons with impaired glucose tolerance and in patients with new-onset diabetes of known duration in the Diabetes Prevention Program (DPP) cohort.

Methods: The DPP recruited persons with elevated fasting glucose (5.3-6.9 mmol/l) and impaired glucose tolerance, and no history of diagnosed diabetes, other than gestational diabetes not persisting after pregnancy. Seven-field, stereoscopic fundus photography was completed a mean of 3.1 years after the development of diabetes in 594 of 878 participants who had developed diabetes during the DPP, and in a random sample of 302 participants who remained non-diabetic.

Results: Retinopathy consistent with diabetic retinopathy was detected in 12.6 and 7.9% of the diabetic and non-diabetic participants, respectively (P = 0.03, comparing prevalence in the two groups). Systolic blood pressure and HbA(1c) were higher at baseline in the diabetic participants who had retinopathy compared with the diabetic participants without retinopathy.

Conclusions: Retinopathy characteristic of diabetes is present in persons with elevated fasting glucose and impaired glucose tolerance and no known history of diabetes. The prevalence of retinopathy is significantly higher in persons who develop diabetes, even within 3 years of diagnosis.