Bariatric surgery and diabetic retinopathy: a systematic review and meta-analysis of controlled clinical studies.

BACKGROUND Uncontrolled studies have indicated appearance or progression of diabetic retinopathy in obese diabetic patients after bariatric surgery. The aim of this systematic review and meta-analysis was to compare the rate of appearance, as well as progression or regression of diabetic retinopathy in studies comparing medical and surgical treatment of obese type 2 diabetes. METHODS AND FINDINGS Intervention effect (new cases of retinopathy, and cases with any change of diabetic retinopathy score) was expressed as odds ratio (OR), with 95% confidence intervals (CIs); change of diabetic retinopathy score was expressed as standardized mean difference (SMD), with 95% CIs. Meta-analyses were performed by a random-effects model according to DerSimonian and Laird. Heterogeneity was assessed through Q and I2 statistics for each comparison, and potential sources of heterogeneity were discussed where appropriate. Appropriate methodology [preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement] was used. Seven studies were analyzed, and incident cases of retinopathy were fewer with bariatric surgery than with medical treatment; change of retinopathy score (three studies) was not different, while only two studies were available on numbers of patients showing progression or regression of retinopathy. Heterogeneity was not significant, and publication bias was not present. CONCLUSIONS Bariatric surgery seems to prevent new cases of diabetic retinopathy, but available studies are not sufficient to support progression or regression of retinopathy. Further studies are needed to draw firm conclusions on the effect of bariatric surgery on diabetic retinopathy.