3.2.4. Diabetic Retinopathy

Diabetic retinopathy is a common microvascular complication of diabetes mellitus [119]. Hyperglycemia, oxidative stress, and advanced glycation end products are all risk factors of diabetic retinopathy [120]. Tea has shown protective e ffects on diabetic retinopathy. In diabetic rats, EGCG could protect the retina by decreasing the level of anion and preventing the formation of acellular capillaries and pericyte ghosts [121]. Also, green tea could protect the nerves of diabetic retinas and regulate the subretinal environment by reducing the production of ROS by increasing glutamate transporter expression, reestablishing intercellular connections, and restoring glutamine/glutamate circulation [122]. In addition, green tea at very low dose could improve antioxidant defense, reduce inflammatory markers, and prevent retinal basement membrane thickening [123]. Further, black tea could delay the development of diabetic cataracts by lowering blood sugar, thereby inhibiting pathological biochemical

indicators [124]. Oolong tea extract could increase plasma retinol levels in diabetic rats [125]. Overall, tea acts as a potent neuroprotector in diabetic retinas.
