Cataract is a leading cause of visual disability and blindness throughout the world. It accounts for 47.8% of the roughly, 37 million blind people in the world. Cataract genesis is influenced by multiple risk factors, such as aging, diabetes mellitus, drugs, trauma, toxins, genetics and other ocular diseases. Among the various causes, oxidative stress is considered to play a key role in the molecular mechanism of cataract formation.
The process of cataract formation is more pronounced and is accelerated in patients suffering from diabetes. Diabetes is a group of metabolic diseases characterized by high levels of blood sugar (hyperglycemia). It results from defects in insulin production and/or insulin action, and impaired function in the metabolism of carbohydrates, lipids and proteins which leads to long term health complications. In diabetic patients, long term damage, dysfunction and failure of different organs, especially the eyes (diabetic retinopathy and cataract), kidneys (diabetic nephropathy), nerves (diabetic neuropathy), heart (myocardial infarction) and blood vessels (atherosclerosis) are related to uncontrolled hyperglycemia.
Osmotic stress may lead to the development of cataract in diabetic individuals. This is due to the accumulation of an osmotically active sugar, sorbitol, in the lens tissue. The influx of glucose into the diabetic lens and its oxidation through the polyol pathway, leads to the accumulation of sorbitol in the lens, which generates an osmotic stress that may be a major contributory factor in the development of diabetic cataract.