Diabetes
There are two types of diabetes. Type I (insulin dependent) and Type II (non-insulin dependent). Type I usually occurs in childhood and is due to the death of insulin producing cells in the pancreas due to an autoimmune response. Type II occurs later on in life and is due to a lack of insulin or a resistance of cells to insulin, it is associated with obesity. Insulin is a hormone released by the pancreas that stimulates the bodies cells to take in glucose to use as energy without it glucose levels in the blood become very high. This affects blood vessels in the body, especially capillaries making them prone to blockage and leakage. When these effects occur in the retina small aneurysms and bleeds occur.
Diabetic changes of the retina
As the retina loses its supply of oxygen nerve cells can die leading to what are called cotton wool spots. Eventually the retina sends out a signal which leads to new blood vessels growing in the retina. These blood vessels are not of the same calibre as retinal vessels and they tend to leak leading to vision loss. Eventually fibrosis at the retinal can occur which leads to a retinal detachment.
It usually takes many years for this to occur and it can be prevented by good control of blood sugar with diabetes medication. If you are controlling your blood sugar well and have a good Hb1ac level you can expect to have little change at the retina.
As well having an eye examination every year, diabetic patients should be enrolled by their GP on a diabetic screening scheme, where photos are taken of their retinas once a year and reviewed by a certified screener.
Diabetics are also more prone to cataracts as the high glucose levels lead to changes in the lens.