Proliferative diabetic retinopathy (PDR) is a complication of diabetes caused by changes in the blood vessels of the back of the eye. If you have diabetes, your body does not use and store sugar properly. High blood sugar levels cause damage to the veins, arteries, and capillaries that carry blood throughout the body. This damage also occurs in the tiny blood vessels in the retina. The retina is the light-sensitive nerve layer that lines the back of the eye.
In PDR, the retinal blood vessels are so damaged they close off. Blood is not properly delivered to the retina. The retina starves of oxygen and nutrients. In response, the retina grows new, fragile blood vessels to try to re-deliver blood to the retina. Unfortunately, these new blood vessels are abnormal and grow on the surface of the retina, so they do not resupply the retina with blood.
Occasionally, these new blood vessels bleed and cause a vitreous hemorrhage. Blood in the vitreous, the clear gel-like substance that fills the inside of the eye, blocks light rays from reaching the retina. A small amount of blood will cause dark shadows and floating objects, while a large bleed might block all vision, leaving only light and dark perception.
As the new blood vessels, they can pull on the retina, causing distortions of the retina and distortions of vision. Sometimes scar tissue grows with these abnormal blood vessels, and the scar tissue can cause the pulling to be more severe. If the pulling is severe, the retina in the center of vision may detach from its normal position and cause vision loss.
Laser surgery may be used to reduce the signals in the retina to grow these abnormal blood vessels. As the signals go away, the abnormal blood vessels start to shrink and the risk of bleeding is reduced. The laser does not eliminate the risk of bleeding, it only reduces it.
When bleeding (vitreous hemorrhage) has already occurred in the eye, the body will usually absorb blood, but that can take days, months, or even years. If the vitreous hemorrhage does not clear within a reasonable time, or if a retinal detachment is detected, a surgery operation called a vitrectomy may be performed. During a vitrectomy, the eye surgeon removes the blood and any scar tissue that has developed, and, often times, performs laser treatment to decrease the chances of any more new abnormal vessel growth.
People with PDR sometimes have no symptoms until it is too late to treat it. The retina may be badly injured before there is any change in vision. There is considerable evidence to suggest that tight control of your blood sugar decreases the chance of developing serious PDR.
Because PDR often has no symptoms, if you have any form of diabetes you should have your eyes examined regularly by an eye doctor.