BACKGROUND Type 2 diabetes mellitus (T2DM) is a well-recognised complication of obesity. One of the microvascular complications of T2DM is diabetic retinopathy (DR). Bariatric surgery has been shown to effectively treat obesity and can induce remission of T2DM. It is not known what effect this improvement may have on pre-existing DR. We aimed to investigate this. METHOD A dual-centre, observer-blinded, case-control study investigated the progression of DR in patients who received Roux-en-Y gastric bypass (treatment group (TG)), compared with controls who received medical therapy (control group (CG)) for their T2DM. Retinal images were taken pre-operatively and approximately 2 years post-operatively for the TG and over a 2-year interval for the CG. Data were collected for confounding variables, including glycaemic control (HbA(1c)) and BMI. RESULTS Forty-five patients were recruited (TG = 21, CG = 24). Groups were significantly heterogeneous. DR showed significant progression for those in the CG (p = 0.03) but not in TG (p = 0.135), no significant difference was found when adjusting for confounding variables (p = 0.480). There was a significant trend in favour of surgery in improvement of glycaemic control (p = 0.017). CONCLUSION The trends within these pilot data may represent a real difference in the progression of DR in patients who have received surgery, compared with medical treatment alone. Due to heterogeneity of group characteristics, further work needs to be done to validate these results. Should there be a true difference, there will be potential cost savings for the National Health Service (NHS) along with a reduced burden of disease for patients.