By Ivan G. Castillo, MD

Proliferative diabetic retinopathy (PDR) is a complication of diabetes caused by changes in the blood vessels of the eye. If you have diabetes, your body does not use and store sugar properly. High blood sugar levels create changes in the veins, arteries, and capillaries that carry blood throughout the body. This includes the tiny blood vessels (capillaries) in the retina, the light-sensitive nerve layer that lines the back of the eye.

In PDR, the capillaries inside the retina are so damaged that they close off. In response, the retina produces a chemical called VEGF. VEGF stimulates the growth (proliferation) of new, fragile blood vessels. Unfortunately, these new blood vessels are abnormal and grow (proliferate) on the surface of the retina, and as a result, 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 floaters, while a larger hemorrhage might block all vision, leaving only light and dark perception.

The new blood vessels can also cause scar tissue to grow. The scar tissue shrinks, wrinkling and pulling on the retina and distorting vision. If the pulling is severe, the macula may detach from its normal position and cause vision loss.

Treating Proliferative Diabetic Retinopathy
Laser surgery may be used to shrink the abnormal blood vessels and reduce the risk of bleeding. An alternative treatment that will shrink the abnormal blood vessels is the injection of anti-VEGF medication into the vitreous. Sometimes anti-VEGF injections are used in combination with laser surgery to shrink the abnormal blood vessels and control the bleeding. The body will usually absorb blood from a vitreous hemorrhage, 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, an operation called vitrectomy can be performed. During a vitrectomy, a retina surgeon removes the hemorrhage and any scar tissue that has developed, and performs laser treatment to prevent new abnormal vessel growth.

Detecting and Preventing Proliferative Diabetic Retinopathy
People with PDR sometimes have no symptoms until it is too late to treat them. The retina capillaries may be badly injured before there is any change in vision. The best way to evaluate the damage to the retinal capillaries is by performing a fluorescein angiogram. During this diagnostic test, a vegetable-based dye is injected into a vein in the arm. The flow of the dye through the retinal capillaries is then recorded by a series of photographs. There is considerable evidence to suggest that rigorous control of blood sugar decreases the chance of developing serious proliferative diabetic retinopathy (PDR).

Because PDR often has no symptoms, if you have any form of diabetes, you should have your eyes examined regularly by an ophthalmologist.