| Proliferative Diabetic Retinopathy As the damage to the capillaries becomes worse, the retina does not get adequate blood flow. Because it is not getting enough blood flow, the eye stimulates the growth of new blood vessels in an attempt to increase the blood flow to the retina. Vascular endothelial growth factor (VEGF) is believed to play a prominent role in this process. The new blood vessels that grow are abnormal, however, and do not supply additional blood flow to the retina. The blood vessels grow from the surface of the retina rather than within the retina. The blood vessels can result in the development of multiple vision-threatening problems within the eye. These blood vessels are abnormally leaky and have a great tendency to bleed (hemorrhage) within the eye. It is possible for a person with diabetes to have extensive blood vessel damage and extensive growth of abnormal new blood vessels in the eye before they notice any change in vision. Hemorrhage from the abnormal blood vessels can occur at any time, and can be mild or severe. If the hemorrhage is severe, the vision can be severely affected. The growth of abnormal blood vessels is also associated with the development of fibrous or scar tissue on the retina. This fibrous or scar tissue can pull on the retina and create distortion of the retina or even retinal detachment which can severely affect the vision. The natural history of proliferative diabetic retinopathy is that the abnormal blood vessels and scar tissue will grow progressively worse and may eventually completely blind the eye. All diabetic patients should be monitored with periodic dilated eye examinations, with particular attention to the retina, to identify the development of any evidence of abnormal blood vessel growth at the earliest possible stage. Laser Treatment for PDR The only known effective treatment for abnormal blood vessel growth in proliferative diabetic retinopathy is laser photocoagulation. Laser treatment is recommended either when the individual has developed significant growth of abnormal blood vessels or in some individuals who are at very high risk for the development of extensive blood vessel growth. The laser is applied in a "panretinal pattern" throughout the periphery of the retina. The purpose of laser treatment is to try to get the abnormal vessels to shrink or regress. Anywhere from 1000 to 1500 laser "spots" are applied to the retinal periphery. We generally combine this with cryopexy treatment in a single session. In some individuals, additional laser treatments may be necessary to attempt to control the proliferative diabetic retinopathy. Laser treatment does not cure the disease. Even after initially successful laser treatment, the underlying diabetic disease continues, more blood vessel damage can develop, and abnormal blood vessel growth can recur in the future. If this occurs, laser treatment can usually be repeated, or vitrectomy surgery can be performed. Laser treatment can decrease but not eliminate the chances of developing visual loss due to proliferative diabetic retinopathy. Some people will lose vision despite timely and appropriate laser treatment. In people who develop severe hemorrhage or retinal detachment due to the blood vessel growth, laser treatment alone may not be effective, and vitrectomy surgery may be necessary to save vision. Side Effects of Laser Treatment Because of the amount of treatment required, we often anesthetize or in some cases, the patient can be put under general anesthesia. Diabetic macular edema can occasionally develop or grow worse soon following panretinal laser treatment. This can cause the central vision to blur. Some people will notice a decrease in their peripheral vision after panretinal laser treatment. Some people will notice a decrease in their night vision or adaptation to dark following laser treatment. Some people may notice trouble focusing with their near vision following laser treatment, and occasionally, the pupil may remain partially dilated following laser treatment. As long as any abnormal blood vessels remain in the eye, hemorrhage can still occur. As the laser treatment is causing the abnormal blood vessels to go away, occasionally the associated scar tissue can grow worse and still place traction on the retina or even cause retinal detachment. The major cause of visual loss following laser treatment of proliferative diabetic retinopathy is failure of the retinopathy to respond to the laser treatment adequately or progression of the disease despite laser treatment. The above side effects do not occur in all individuals, and many individuals notice none of the above side effects. Once you have developed proliferative diabetic retinopathy, your chances of losing vision are much greater without treatment than with treatment. Cryopexy (Freezing) for PDR Cryopexy is another way to cause peripheral retinal destruction to decrease the production of VEGF and other growth factors responsible for PDR. It is applied to the sclera (white part of eye) to the peripheral retina where it is difficult to treat with laser. We often combine this treatment with laser PRP to have a better total effect, as this can treat more peripherally without the need for perfect visualization. Avastin for Severe PDR Avastin is an anti-cancer drug which binds to and inactivates VEGF. Because this is found in elevated levesl in patients with proliferative diabetic retinopathy, it is occasionally used in the treatment of PDR. Since this is an off-label use of the drug and is not currently covered by insurance, only some patients will elect this treatment. For now, it is probably best given in additional to standard therapy or when standard therapy fails. |
