GCG and diabetic retinopathy: RoB 2: Cochrane Risk of Bias 2 tool; SAP: Statistical analysis plan; BMI: Body mass index; CI: Confidence interval; CV: Cardiovascular; CVOT: Cardiovascular outcome trial; DN: Diabetic nephropathy; DR: Diabetic retinopathy; eGFR: Estimated glomerular filtration rate; EQW: Exenatide once weekly; GLP-1 RA: Glucagon-like peptide-1 receptor agonist; HbA1c: Hemoglobin A1c; HR: Hazard ratio; LSMD: Least squares mean difference; QW: Once weekly; RCT: Randomized controlled trial; RRT: Renal replacement therapy; T2DM: Type 2 diabetes mellitus