Retinopathy affects on average 30% of all patients with diabetes. Good glycaemic control delays the onset and progression of retinopathy in subjects with both type 1 and type 2 diabetes. However, the incidence of retinopathy has not been declining in type 1 diabetes over the last decades, even if visual acuity may be better preserved. As many as 20% of the patients with type 2 diabetes mellitus have already retinopathy at the time of diagnosis of diabetes. Diabetic macular edema (DME) is a serious manifestation of diabetic retinopathy that produces loss of central vision. Data from the Wisconsin Epidemiological Study of Diabetic Retinopathy (WESDR) estimate that after 15 years of known duration of diabetes the prevalence of DME is 20% in patients with type 1 diabetes mellitus, 25% in patients with type 2 diabetes who are treated with insulin, and 14% in the patients with type 2 diabetes who are not treated with insulin. Concerning the natural history a previous study has shown that 53% of the eyes with DME involving the centre of the macula, lost two or three lines of visual acuity over a two year period. In addition, in the Early Treatment Diabetic Retinopathy Study (ETDRS), 33% of untreated eyes available for follow-up at the 3-year visit, all with oedema involving the centre of the macula at baseline, had experienced a 15 or more letter decrease in visual acuity score.