OBJECTIVE To examine the global prevalence and major risk factors for diabetic retinopathy (DR) and vision-threatening diabetic retinopathy (VTDR) among people with diabetes. RESEARCH DESIGN AND METHODS A pooled analysis using individual participant data from population-based studies around the world was performed. A systematic literature review was conducted to identify all population-based studies in general populations or individuals with diabetes who had ascertained DR from retinal photographs. Studies provided data for DR end points, including any DR, proliferative DR, diabetic macular edema, and VTDR, and also major systemic risk factors. Pooled prevalence estimates were directly age-standardized to the 2010 World Diabetes Population aged 20–79 years. RESULTS A total of 35 studies (1980–2008) provided data from 22,896 individuals with diabetes. The overall prevalence was 34.6% (95% CI 34.5–34.8) for any DR, 6.96% (6.87–7.04) for proliferative DR, 6.81% (6.74–6.89) for diabetic macular edema, and 10.2% (10.1–10.3) for VTDR. All DR prevalence end points increased with diabetes duration, hemoglobin A_1c, and blood pressure levels and were higher in people with type 1 compared with type 2 diabetes. CONCLUSIONS There are approximately 93 million people with DR, 17 million with proliferative DR, 21 million with diabetic macular edema, and 28 million with VTDR worldwide. Longer diabetes duration and poorer glycemic and blood pressure control are strongly associated with DR. These data highlight the substantial worldwide public health burden of DR and the importance of modifiable risk factors in its occurrence. This study is limited by data pooled from studies at different time points, with different methodologies and population characteristics.

Several studies demonstrate the role of adipose mesenchymal stem cells (ASCs) in angiogenesis. The angiogenic mechanism has been ascribed to paracrine factors since these cells secrete a plenty of signal molecules and growth factors. Recently it has been suggested that besides soluble factors, extracellular vesicles (EVs) that include exosomes and microvesicles may play a major role in cell-to-cell communication. It has been shown that EVs are implicated in the angiogenic process.

The onset of diabetic retinopathy is characterized by morphologic alterations of the microvessels, with thickening of the basement membrane, loss of inter-endothelial tight junctions and early and selective loss of pericytes, together with increased vascular permeability, capillary occlusions, microaneurysms and, later, loss of endothelial cells (EC). A key role in the evolution of the disease is played by pericytes, specialized contractile mesenchymal cells of mesodermal origin, that, in capillaries, exert a function similar to smooth muscle cells in larger vessels, regulating vascular tone and perfusion pressure. Thickening of the basement membrane, together with systemic and local hypertension, hyperglycaemia, advanced glycation end-product formation and hypoxia, may disrupt the tight link between pericytes and EC causing pericyte apoptosis, while endothelium, deprived of proliferation control, can give rise to new vessels. Pericyte dropout has great consequences on capillary remodelling and may cause the first abnormalities of the diabetic eye which can be observed clinically. Hyperglycaemia and local hypertension are known to be a direct cause of pericyte apoptosis and dropout, and intracellular biochemical pathways of the glucose metabolites have been explored. However, the exact mechanisms are not yet fully understood and need further clarification in order to develop new effective drugs for the prevention of retinopathy.

OBJECTIVE—To study time course changes in knowledge, problem solving ability, and quality of life in patients with type 2 diabetes managed by group compared with individual care and education. RESEARCH DESIGN AND METHODS—We conducted a 5-year randomized controlled clinical trial of continuing systemic education delivered by group versus individual diabetes care in a hospital-based secondary care diabetes unit. There were 120 patients with non–insulin-treated type 2 diabetes enrolled and randomly allocated to group or individual care. Eight did not start and 28 did not complete the study. The main outcome measures were knowledge of diabetes, problem solving ability, quality of life, HbA_1c, BMI, and HDL cholesterol. RESULTS—Knowledge of diabetes and problem solving ability improved from year 1 with group care and worsened among control subjects (P < 0.001 for both). Quality of life improved from year 2 with group care but worsened with individual care (P < 0.001). HbA_1c level progressively increased over 5 years among control subjects (+1.7%, 95% CI 1.1–2.2) but not group care patients (+0.1%, −0.5 to 0.4), in whom BMI decreased (−1.4, −2.0 to −0.7) and HDL cholesterol increased (+0.14 mmol/l, 0.07–0.22). CONCLUSIONS—Adults with type 2 diabetes can acquire specific knowledge and conscious behaviors if exposed to educational procedures and settings tailored to their needs. Traditional one-to-one care, although delivered according to optimized criteria, is associated with progressive deterioration of knowledge, problem solving ability, and quality of life. Better cognitive and psychosocial results are associated with more favorable clinical outcomes.