DPP4 and diabetic retinopathy: The HRs of biguanide use vs. DPP-4 inhibitor use for diabetic retinopathy, nephropathy, neuropathy, and other conditions were 0.93 (0.71–1.22), 0.97 (0.61–1.54), 0.76 (0.34–1.67), and 1.04 (0.59–1.84), indicating no significant difference.