Diabetic Retinopathy (#1 cause), macular degeneration and Cataracts are all associated with a HIGH CARB DIET!
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By far the leading cause of blindness in the world is Diabetes. Diabetes, with the exception of the relatively rare Juvenile Diabetes is caused by High Carbohydrate Diets. Diabetes does this because the chronically high sugars associated with a high carbohydrate diet damage the nerves in the retina of the eye.
The next most common cause is Cataracts which are also associated with high carbohydrate diets. Eating something high in carbohydrates will spike your glucose level. When glucose is high it readily seeps into the lens of the eye which has no blood vessels in it and is one of the few organs that rely solely on glucose for fuel. When the glucose in the lens gets high the body converts it to sorbitol which in turn triggers protein production through a complex pathway leading to cataracts and eventually blindness.
And finally the tragic blindness of Macular Degeneration is also associated with a high carbohydrate diet through a complex mechanism that has not been fully identified yet. This prospective study showed a nice stair-step rise in the risk of macular degeneration as the glycemic index of a food went up. (All foods with a high glycemic index are carbohydrates.)
The entire white of the eye is covered by a transparent membrane called the blubar conjunctiva. when part of this membrane thickens and this thickened area starts growing over the cornea of the eye it is called a Ptyrigium. These growths have been shown to have higher concentrations of Insulin-like Growth Factor (IGF) receptors in them. People who eat more carbohydrate tend to have higher insulin levels and adult diabetics have very high insulin levels. There is no scientific controversy about this. Insulin also stimulates IGF receptors causing the cells they are on to grow and divide. Thus a very plausable theory is that the high insulin levels of a high carbohydrate diet help drive the spread of these growths over the eye, sometimes severe enough to cause blindness.
In short, there is nothing better you can do for your eyes than AVOIDING CARBOHYDRATES!