Salvianolic acid, primarily derived from the herb Salvia miltiorrhiza (Danshen), has garnered scientific interest for its potential protective effects in diabetic retinopathy (DR). Preclinical studies, mostly in animal models and cell cultures, indicate that salvianolic acid exhibits antioxidant, anti-inflammatory, and anti-apoptotic properties, which are relevant to the pathophysiology of DR. DR is characterized by oxidative stress, inflammation, and microvascular damage in the retina, and salvianolic acid appears to counteract these processes by scavenging free radicals, inhibiting pro-inflammatory cytokines, and protecting retinal cells from hyperglycemia-induced injury.

Some studies have demonstrated that salvianolic acid B, a major component, can reduce retinal vascular leakage, inhibit VEGF expression, and prevent retinal cell death in diabetic animal models. These findings suggest a mechanistic basis for its use in DR. However, clinical evidence in humans is very limited; most data come from laboratory research, with few small-scale or low-quality clinical trials available. Traditional Chinese medicine has used Danshen preparations for vascular disorders, but the specific use of isolated salvianolic acid for diabetic retinopathy is not well documented in traditional sources.

In summary, while there is some scientific rationale and preclinical evidence supporting the use of salvianolic acid for diabetic retinopathy, robust human clinical studies are lacking. The overall evidence quality is low, justifying a score of 2 on the evidence scale.