title: The Impact of Bariatric Surgery on Diabetic Retinopathy: A Systematic Review and Meta-Analysis.
abstract: BACKGROUND
  Significant reductions in glucose control immediately post bariatric surgery in patients with longstanding poor glycemic control can lead to the paradoxical progression of diabetic retinopathy (DR) in susceptible individuals. Bariatric surgery results in dramatic and immediate diabetic control postoperatively. We aimed to systematically review the literature to assess the effect of bariatric surgery on DR.
  
  
  METHODS
  A comprehensive search of electronic databases (e.g., MEDLINE, EMBASE, SCOPUS, Web of Science, and the Cochrane Library) was completed. All randomized controlled trials, non-randomized comparison study, and case series were included. Inclusion criteria included English-speaking studies, enrolling ≥ 5 patients, and contained ophthalmological data on outcome of DR pre- and post bariatric surgery. Two independently reviewers screened abstracts, reviewed full text versions of all studies classified, and extracted data. All comparison studies included in the meta-analysis were assessed independently by two reviewers for methodological quality using the Cochrane Risk of Bias (RoB) tools. Disagreements were resolved by re-extraction, or third-party adjudication. Where possible and appropriate, a meta-analysis was conducted.
  
  
  RESULTS
  A total of 277 studies were identified using our search criteria for screening. Four primary studies (n = 148 patients) met our inclusion criteria and were included in the systematic review. These included no randomized controlled trials and four non-randomized case series. Patients with no preoperative DR (n = 80), following bariatric surgery, an average of 92.5 ± 7.4 % remained disease free, while 7.5 ± 7.4 % of patients progressed to DR. Patients with diabetic retinopathy preoperatively (n = 68), following bariatric surgery, an average of 57.4 ± 18.5 % of patients had no change, 23.5 ± 18.7 % of patients had progression, and 19.2 ± 2.9 % of patients had improvement in their disease.
  
  
  CONCLUSIONS
  Progression of diabetic retinopathy is a significant issue postoperatively following bariatric surgery. Patients with a diagnosis of DR prior to surgery are at increased risk of further progression in their disease and should receive adequate counseling and evaluation prior to undergoing a surgical procedure. However, the few primary studies in this systematic review limit any conclusion. Further studies are needed to further evaluate these results.
authors.affiliation: Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Douglas
authors.initials: D
authors.lastname: Cheung
authors.forename: Noah J
authors.initials: NJ
authors.lastname: Switzer
authors.forename: David
authors.initials: D
authors.lastname: Ehmann
authors.forename: Christopher
authors.initials: C
authors.lastname: Rudnisky
authors.forename: Xinzhe
authors.initials: X
authors.lastname: Shi
authors.forename: Shahzeer
authors.initials: S
authors.lastname: Karmali
mesh_terms: D050110:Bariatric Surgery; D003930:Diabetic Retinopathy / Q000150:complications* / Q000628:therapy*; D018450:Disease Progression; D006801:Humans