Controversy exists on how the functional impairment triggered by diabetes affects the retinal vascular structure, leading to diabetic retinopathy (DR). DR remains a main cause of blindness in United Kingdom with thousands of new cases per year. Diagnosing DR early is crucial for planning the treatment more effectively, before the retina of the eye is severely affected. In this study we investigated the hypothesis that significant vascular changes occur during the progression of diabetes until the first lesions appear in the retina (background retinopathy). The analysis is approached from a novel perspective in which the selected images for pre-/post-DR come from the same patients who have progressed from diabetes to DR. The measurements were analyzed using a statistical model. Veins' and arteries' widths and also arteries' angles were found to differ significantly between the two cases, but no statistical significance was observed for the veins' angles.