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  • br Diabetic retinopathy Diabetic retinopathy is a severe sig

    2023-01-16


    Diabetic retinopathy Diabetic retinopathy is a severe sight-threatening complication associated with diabetes mellitus. It is one of the most common causes of preventable blindness in the world. The risk of developing microvascular diabetic complications increases in diabetic patients with an increase in the duration of time for which they had been suffering with diabetes. This statement is supported by evidential statistical data regarding the occurrence of diabetic retinopathy. This data concludes that the chances of development of diabetic retinopathy in the patients suffering with diabetes mellitus from the past 5years were around 17% whereas the patients who were diagnosed with diabetes since 15years or more had approximately 97.5% chance to develop this complication. Also, the clinical sub-type of diabetes (viz., type I diabetes or type II diabetes) is considered as a determining factor in the development of diabetic retinopathy. Various studies conducted regarding this respect have stated that considerable amount of damage is produced to the retinal Pirinixic Acid of patients within 20years of being diagnosed with type I diabetes mellitus. However, patients of type II diabetes mellitus are prone to the development of diabetic retinopathy quite early in the course of the parent disorder, with some cases being reported as early as seven years preceding the diagnosis of type II diabetes mellitus in the patient. Hyperglycemia is responsible for the induction of various pathological pathways (such as increased flux of polyol pathway, increased production of advanced glycation end-products, overactivation of protein kinase C and liberation of various inflammatory mediators), due to which the epithelial cells of the retinal blood vessels get severely damaged. The damaged epithelial cells act as harbinger for the activation of numerous other pathological mechanisms (such as overexpression of various growth factors, oxidative stress-induced damage and various other hemodynamic changes), which ultimately result in epithelial dysfunction. This hyperglycemia-induced epithelial dysfunction is regarded as the fundamental reason for the advent of microvasculature complications in diabetes. The dysfunction of retinal epithelial cells acts as a precursor for various other pathological conditions such as thickening of the basal membrane of endothelium, increase in the permeability of endothelial cells (to the extent of leakage), regulation of an intense inflammatory response and mediation of apoptosis of endothelial cells [6–8]. Clinically, diabetic retinopathy is divided into two stages — non-proliferative diabetic retinopathy and proliferative diabetic retinopathy. Non-proliferative diabetic retinopathy is the initial stage of this disorder which is generally characterized by the formation of microaneurysms. Microaneurysms are basically small regions in the blood vessels presented with abnormal dilatation. This is speculated to be caused due to the various angiogenic factors released during hyperglycemia-induced inflammatory response. The microaneurysms are the primary site of damage of the blood vessels, after which the consequent inflammatory responses lead to a cascade of other molecular changes responsible for the conversion of non-proliferative diabetic retinopathy into proliferative diabetic retinopathy. It is the advanced stage of this complication. Neovascularization and macular edema are the chief characteristic events of this stage. Neovascularization (or angiogenesis) is defined as the process of formation of new blood vessels on the surface of the pre-existing ones. Since the blood vessels formed during this process are not fully developed to withstand the extreme conditions of oxidative stress and inflammatory responses induced by hyperglycemia, prevalent in the retina during diabetes mellitus, the newly developing blood vessels rupture. This event results in leakage of the contents of blood vessels into the vitreous chamber, resulting in vitreous hemorrhage — a characteristic indication of the progression of diabetic retinopathy. Further stress on the retina due to the above described pathological conditions result in retinal detachment. It is the terminal event of diabetic retinopathy, due to which vision is lost [1,9].