Curcuminoids, the active polyphenolic compounds found in turmeric (Curcuma longa), have been investigated in preclinical and limited clinical studies for their potential in managing diabetic retinopathy. The scientific rationale is based on curcuminoids’ antioxidant, anti-inflammatory, and anti-angiogenic properties, which may counteract the oxidative stress, chronic inflammation, and abnormal blood vessel formation characteristic of diabetic retinopathy.

Experimental studies (in vitro and in animal models) have shown that curcumin can inhibit high glucose-induced retinal cell apoptosis, reduce inflammatory cytokines, and prevent vascular endothelial growth factor (VEGF) expression, all of which are implicated in the pathogenesis of diabetic retinopathy. For example, studies in diabetic rats have demonstrated that curcumin supplementation attenuates retinal oxidative damage and vascular leakage.

Human evidence is limited. A few small clinical trials and pilot studies have examined curcumin or curcuminoid supplementation in patients with diabetic retinopathy, with some reporting improvements in retinal microcirculation, vascular leakage, or inflammatory markers, but these studies are generally of low quality, with small sample sizes and short durations.

In summary, while there is a plausible biological basis and supportive animal data, high-quality clinical trials demonstrating clear benefits in human diabetic retinopathy are lacking. Thus, the evidence is preliminary (rated 2/5), and curcuminoids cannot yet be considered a validated treatment for diabetic retinopathy.