Sir,

We read with interest the paper by Chen et al,1 based on a retrospective study of 102 diabetic patients with no retinopathy (68%) or pre-existing retinopathy (32%) re-evaluated up to 4 years after bariatric surgery. Chen et al1 found that retinopathy appeared or progressed in 24% of patients, while retinopathy of any degree remained stable in 72% of patients and improved in 4% of patients. Young age, male gender, high pre-operative HbA1c, and presence of pre-operative retinopathy were the significant predictors of worsening postoperatively.

Chen et al1 conclude that bariatric surgery does not prevent progression of DR, and that future prospective studies with long follow-up are required to clarify the duration of risk.

Similar results, but also contrasting results, have been reported in the literature, leading to opposite interpretations.2, 3 One should consider first that all these findings came from uncontrolled studies, and therefore one might hypothesize that similar or even worse results might apply for diabetic patients receiving only medical treatment instead of bariatric surgery; it is known that rapid improvement in glycaemic control may cause a paradoxical worsening in DR.1 Second, in a large cohort study on about 4600 diabetic patients undergoing bariatric surgery, patients who experienced type 2 diabetes remission had 29% lower risk of incident microvascular disease compared with patients who never remitted. Among patients who experienced a relapse after remission, the length of time spent in remission was inversely related to the risk of incident microvascular disease.4

Nevertheless, these data suggest that bariatric surgery, if any, can prevent appearance of retinopathy, but is unable to prevent deterioration of pre-existing retinopathy, as outlined in a meta-analysis that took into consideration only controlled studies.5