Background and Objectives: Nowadays, every tenth adult in the world suffers from diabetes mellitus (DM). Diabetic retinopathy (DR) is the most common microvascular complication of type 2 DM (T2DM) and a leading cause of acquired blindness in middle-aged individuals in many countries. Previous studies have identified associations of several gene polymorphisms with susceptibility to microvascular complications of DM in various worldwide populations. In our study, we aimed to test the hypothesis of the associations of single nucleotide polymorphisms (SNP) of the VEGF (−2549I/D), RAGE (−429T/C and −374T/A), TCF7L2 (rs7903146), and ITGA2 (BglII) genes with a predisposition to DR among T2DM patients in the Kazakhstan population. Materials and Methods: We conducted a case–control study comparing the genotype distribution and allele frequencies between groups of DR patients (N = 94), diabetic patients without DR (N = 94), and healthy controls (N = 51). Genotypes were identified using the PCR-RFLP method. Results: In all cases, the genotype distribution corresponded to the Hardy–Weinberg equilibrium. The groups of diabetic patients with and without DR did not significantly differ in the genotype distribution of the SNPs studied. Differences between both groups of diabetic patients and healthy controls in four out of five SNPs were also not significant. At the same time, both groups of diabetic patients differed significantly from healthy controls in genotype distribution (p = 0.042 and 0.005, respectively) and allele frequencies (p = 0.021 and 0.002, respectively) of the BglII polymorphism in the ITGA2 gene. After adjusting for multiple comparisons, the differences between the group of diabetic patients without DR and the control group remained significant (pBonf = 0.027 for genotypes and pBonf = 0.009 for alleles). The BglII− allele was associated with diabetes: OR = 1.81 [1.09–2.99] for DR patients, and OR = 2.24 [1.34–3.75] for diabetic patients without DR. The association was also observed in the subset of Kazakhs. Conclusions: This study shows that the BglII polymorphism in the ITGA2 gene can be associated with T2DM but not with DR. According to our data, the risk allele for diabetes is the wild BglII− allele, and not the minor BglII+, which is considered as risky for DR.

Blindness and low vision, as a social medical problem, occupy one of the leading places in both healthcare and the state economy. Diabetic retinopathy (DR) is a vision-threatening microvascular disease, the most common diabetes complication that affects the retina, causing blindness among working-age adults in developed countries. Difficulties in determining the starting, key pathogenetic links and early diagnosis of this disease do not allow to accurately determine the initial moment of occurrence, and known treatment methods are aimed, as a rule, at slowing down the pathological process. Purpose. Analysis of literature data on the clinical and diagnostic features of diabetic retinopathy. Material and methods. To analyze the literature, information was searched on this problem up to 10 years deep in PubMed / MEDLINE, PMC, Web of Since. For the search, the following terms were used individually or in combination: "diabetes mellitus", "diabetic retinopathy", "diabetic vasculopathy", "optical coherence tomography", "fluorescence angiography", "complications". The search criteria were key studies related to diabetic retinopathy, vasculopathy: meta-analyzes, original studies, retrospective and cohort studies. Results and discussions. Oxygen from the capillary layer of the choroid through the Bruch membrane and retinal pigment epithelium (RPE) gets to the outer retinal layers. Due to complications in the bloodstream, nutrition is impaired which leads to diabetic retinal changes. It is advisable and necessary to study changes in the structures of the choroid in large samples using angio-OCT, since changes in the choroid can be the primary prognostic markers of the development of diabetes in the absence of clinical manifestations of diabetic retinopathy. Conclusion. Changes in the structure of the choroid can become a marker for predicting the development of DR in patients with type 2 diabetes, more accurately and quickly establish a diagnosis in the early stages of the disease, and prescribe appropriate therapy in a timely manner. As a result, patients receive timely care and treatment costs will decrease. Keywords: diabetes mellitus, diabetic retinopathy, choroid, diabetic choriopathy, OCT angiography, choroid structures.