The effect of curcumin-piperine on cardiometabolic, inflammatory and oxidative stress factors and macular vascular density in optical coherence tomography angiography (OCTA) in patients with non-proliferative diabetic retinopathy: Study protocol for a randomized, double-blind controlled trial

Curcumin is a safe phytochemical with antioxidant, anti-inflammatory, antidiabetic, and lipid-lowering effects. This study aims to investigate the efficacy of curcumin-piperine in non-proliferative diabetic retinopathy. In this double-blind randomized trial, 60 diabetic retinopathy patients after meeting the inclusion criteria will be randomly assigned to two groups of curcumin-piperine supplementation (1000 mg per day for 12 weeks) or receiving placebo. The density of small blood vessels in the retina by optical coherence tomography angiography (OCTA), fasting blood glucose, triglyceride, renal indices (blood urea nitrogen and creatinine), high-sensitivity C-reactive protein, total antioxidant capacity, total oxidant status, body mass index, waist circumference, and weight will be measured. If the beneficial effects of curcumin on diabetic retinopathy are observed, this safe, this natural and inexpensive herbal supplement can be considered a therapeutic solution in these patients.