Beneficial effects of phytochemicals in diabetic retinopathy: experimental and clinical evidence

Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus and a major preventable cause of blindness. Strict control of blood glucose, blood pressure, and lipid profiles are the pivotal criteria to reduce the risk of developing DR. Although timely intervention with laser photocoagulation therapy could mitigate the progression of DR, it may not significantly improve visual acuity. Therefore, invasive surgical interventions such as vitrectomy are sometimes the only option to treat or manage advanced stages of DR. However, the risk of intra-ocular infections outweighs the benefits of the surgery. Newer therapies such as intraocular injection of anti-vascular endothelial growth factor (VEGF) antibody and steroids serve as a viable option for the treatment of DR. However, several clinical studies that assessed the long-term efficacy and safety of this therapy have yielded inconclusive results. Therefore, there is an urgent need to develop potent and safe drugs for the effective management of DR. In this review, we discuss various plant-derived small molecules (phytochemicals) that have been investigated for retinal cytoprotective effects in pre-clinical and clinical studies. Furthermore, we highlight the caveats on using phytochemicals for the management of DR.