Generally, DM is caused by insufficient insulin secretion in the body; however, the other biological mechanisms remain unclear. Long-term illness in patients with DM damages various organs in the body, such as the eyes, kidneys, and heart, seriously affecting organ function. Nowadays, the quality of life of people has improved significantly, eating habits have changed, sugar intake is increasing, and the number of patients with DM is increasing. Statistics show that in 2017, the number of patients with DM worldwide reached 425 million (aged 20-79 years), which will exceed 600 million in 30 years; moreover, patients in low- and middle-income countries, such as China and India, account for 80 percent of the total DM population (1). According to the WHO, patients with DM worldwide increased to 366 million in 2011, which is expected to increase to 500 million in 2025, with more than 150 million patients experiencing ocular complications, such as diabetic retinopathy (DR) (2, 3). DR is a form of ocular microangiopathy and the most serious DM-related complication; it seriously endangers the health of patients with DM (4). DR pathogenesis includes increased endothelial cells in the eye capillaries, increased intimal thickness, damaged pericytes, microangioma, and damaged blood-retina barrier due to increased permeability of the blood vessels, microvascular obstruction, and neovascularization (NV) (5, 6). Currently, the prevalence of DR is 34.6% worldwide; however, it is higher in some developed countries, reaching 40.3% (7). The proportion of patients with type 1 and 2 DM suffering from blindness due to DR is 3.6% and 1.6%, respectively (8). DR is associated with significantly reduced living standards, huge medical costs, and increased social burden (9, 10).
Many anti-vascular endothelial growth factor (VEGF) drugs exist; however, the use of therapeutic drugs is strictly controlled. The main drugs recommended for treating DM-related visual complications are ranibizumab and aflibercept.