Introduction
Diabetic retinopathy (DR) is one of the well-known diabetes mellitus complications that influence human eyes. This condition is characterized by vision loss and blindness because of retinal microvascular damage of blood vessels. Diabetes leads to abnormal changes in glucose levels in the blood, which results in unstable capillaries. Vascular abnormalities include hyperpermeability, hypoperfusion, and neoangiogenesis and lead to changes either functional or anatomical in glial cells and retinal neurons.2 During the last several decades, the diabetic epidemic has already become a global health concern, estimating about 422 million people with diabetes today and predicting about 629 million by 2045.3 In the majority of cases, the populations of low-income and middle-income countries suffer from the diabetes burden. However, the citizens of developed countries should not be ignored. Genome wide association studies (GWAS) were used to identify DR-associated genes to improve an understanding of this disease pathogenesis.4 In addition to diabete
s as the main risk factor, such conditions as high blood pressure, cholesterol, tobacco smoking, and pregnancy must be underlined.
From the clinical point of view, DR can be of two types: non-proliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR). NPDR occurs in the early stage of DR when blood vessels leak and cause the retina swell, also known as macular edema. The severity of this condition is classified from mild to severe: mild NPDR includes microaneurysms, moderate NPDR hemorrhages and hard exudates, and severe NPDR intraretinal hemorrhage and venous beading.2 In NPDR patients, new blood vessels are not able to grow but dilate in irregular forms. PDR is defined as a more advanced stage due to neovascularization, the experience of serious vision impairments. The creation of new abnormal retinal vessels provokes vitreous hemorrhages, tractional retinal detachment, and refractory glaucoma.2 Compared to NPDR when the patients vision is blurry, PDR causes a number of new specks or colored spots (red blobs) in vision.