Does bariatric surgery prevent progression of diabetic retinopathy?
Reviewed by Sofia Rokerya

The authors report a retrospective observational study of T2DM patients who underwent bariatric surgery between 2009 and 2015. Preoperative and postoperative weight, HbA1c, and annual diabetic retinopathy (DR) screening results were obtained from medical records. Patients with preoperative retinal screening and at least one postoperative retinal screening were eligible for analysis. Multivariate analysis was used to explore significant clinical predictors on postoperative worsening in DR. A total of 102 patients were found to be eligible for analysis and were followed up for four years. The median age was 55 years and the majority were female (67%). The most common surgical procedure undertaken was Roux-en-Y gastric bypass (n=69, 67%), followed by sleeve gastrectomy (n=14, 14%), gastric band (n=12, 12%), mini bypass (n=4, 4%), and gastric balloon (n=3, 3%). The median preoperative HbA1c of the cohort was 61mmol/mol with a median weight of 123kg. The median duration of diabetes, defined as the time in years from diagnosis to bariatric procedure, was six years in the cohort. Following bariatric surgery, 86% of patients experienced an improvement in HbA1c; 42% achieving normalised HbA1c. There was no correlation between HbA1c changes and type of bariatric procedure undertaken (P=0.215, 0.324, 0.246 respectively). The median weight postoperatively was 103kg with a weight loss of 22kg (18%). Preoperatively 68% of patients had no DR, 30% had background retinopathy, 1% pre-proliferative retinopathy, and 1% proliferative retinopathy. Ninety-four percent of patients had no maculopathy preoperatively vs. 6% with maculopathy. Three percent of patients had previous photocoagulation treatment. At the first postoperative visit, 19% of patients developed new DR, 70% were stable and 11% improved. These proportions remained similar for each postoperative visit over time. Regarding the evolution of maculopathy postoperatively, 88% (n=90) of patients with no maculopathy remained stable. Three percent (n=3) of patients with maculopathy improved to no maculopathy, and 3% (n=3) remained the same. Incidence of new maculopathy was 6% (n=6). It was reported that a 46-year-old male who had background retinopathy in one eye and no maculopathy preoperatively, developed bilateral maculopathy requiring treatment within two years of undergoing bariatric surgery. This was associated with a rapid reduction in his HbA1c from 112 to 37mmol/mol within 12 months. The study concluded that bariatric surgery does not prevent progression of DR. Young age, male gender, high preoperative HbA1c, and presence of preoperative retinopathy were the significant predictors of worsening postoperatively. The incidence of developing new DR at each postoperative visit ranged from 19-7%, with 10-5% of patients maintaining deterioration from previous screening. The results support the current UK NHS diabetic eye screening programme recommendations that all patients should be screened regularly if there has ever been a diagnosis of diabetes, even if they are in remission due to an intervention such as bariatric surgery. Future prospective studies with prolonged follow-up are required to clarify the duration of risk. Limitations of the study: Retrospective nature, lack of control group, lack of consideration to variables such as blood pressure and nephropathy. Strengths of the study: Large cohort and long follow-up, large number of variables taken into account, quality assured NSC grading system used to classify diabetic retinopathy. 

Does bariatric surgery prevent progression of diabetic retinopathy?
Chen Y, Laybourne JP, Sandinha MT, et al.
EYE
2017;31:1131-9.