Circulatory System

• The human circulatory system is a closed system. This means that our blood is pumped from the heart and returned to the heart. Red blood cells with oxygen are pumped from the heart into large arteries. As it moves through the body, it moves into smaller and smaller arteries until it reaches the capillaries. The capillaries are very small. They allow the oxygen from the red blood cells to diffuse into the tissues of the eye. The red blood cells then return to the heart in veins where their oxygen can be replenished.
  
  

Damage to the Eye

• The retina requires a constant supply of oxygen from the red blood cells. As capillary non-perfusion continues, an optometrist or ophthalmologist can see blood and protein leaking into the retina during an eye examination. This is known as diabetic retinopathy. The National Eye Institute describes in detail the stages of diabetic retinopathy. These include mild non-proliferative, moderate non-proliferative, severe non-proliferative, and proliferative diabetic retinopathy.
  
  

What a Patient Sees

• In the early stages of diabetic retinopathy, mild and moderate non-proliferative, the patient may not experience any vision problems. This is good because the patient can still see. However, it is unfortunate because the patient may be unaware that their eyes are experiencing irreversible damage. As diabetic retinopathy develops into severe and proliferative diabetic retinopathy, the patient begins to experience areas of their visual field that are blacked out by blood or damaged rod and cone cells. By the time the patient can see the missing portions of their vision, significant eye damage has already occurred. This is why it is imperative that patients with diabetes receive an annual dilated eye examination from an optometrist or an ophthalmologist.
  
  

Blindness From Capillary Non-Pefusion

• Longstanding capillary non-perfusion causes the retina in the eye to become starved for oxygen. As a result, the retina produces new blood vessels that "proliferate" leading to proliferative diabetic retinopathy. These new blood vessels leak blood. This blood causes the retina to scar and detach. The retina detachment that ensues can cause the patient to go blind in the affected eye.
  
  

Preventing Capillary Non-Perfusion in the Eye

• The longer someone has diabetes, the more likely they are to have diabetic retinopathy from capillary non-perfusion. While this cannot be completely prevented, the risk can be lowered. The more that the patient's blood sugar fluctuates or runs high, the more damage occurs to the cells that line the arteries, resulting in less blood reaching the capillaries. Maintaining good blood sugar control through proper diet, exercise, and the use of prescribed diabetic medications will minimize the patient's risk of developing diabetic retinopathy from capillary non-perfusion in the eye.