The most common vision disorder in people with diabetes is diabetic retinopathy. This involves damage to the blood vessels in the retina, which is the light-sensitive tissue at the back of the eye that translates light into electrical impulses that the brain interprets as vision. It is a complex disorder, and it is generally thought to be triggered by a combination of biochemical, metabolic, and hematologic abnormalities:

• High blood glucose levels may gradually change the metabolism of cells in the retinal blood vessels.
• Diabetes-related biochemical changes may make the blood platelets stickier than in non-diabetic individuals.
• The retinal blood vessels may narrow, or become constricted.

When these abnormalities exist, certain cells inside the retinal blood vessels die, leading to altered blood flow, increased permeability of the blood vessels, and the growth of certain components of blood vessels. As a result, tiny blister-like growths appear on the blood vessels, which may leak. When new blood vessels begin to grow into the retina to increase blood flow, the disease is said to be in the “proliferative” stage. The new blood vessels often leak blood and protein into the fluid inside the eye, impairing vision. At the extreme, the new blood vessels may grow into the vitreous and cause it to detach from the retina, which causes severe visual loss or blindness.

There are usually no symptoms accompanying this process until vision is lost. That's why regular eye exams are so important for people with diabetes. When detected early, diabetic retinopathy can be successfully treated.

Sources:

• NIDDK. Prevent diabetes problems: Keep your eyes healthy. May 2000.
• National Eye Institute. Facts about diabetic eye disease. June 2000.