What is Proliferative Diabetic Retinopathy?
Proliferative diabetic retinopathy (PDR) is a serious complication of diabetes mellitus. In this situation, damage to the retinal blood vessels leads to the secretion of a substance called vascular endothelial growth factor (VEGF). VEGF causes abnormal blood vessels to grow on the surface of the retina and elsewhere in the eye. These vessels bleed easily and may also pull on the retina, causing retinal traction and detachment. They often grow to the point where they threaten vision even without the individual knowing that there is anything wrong. This is one of the reasons that it so important for diabetics to have eye examinations at regular intervals.
When the abnormal blood vessels bleed, the blood ends up in the vitreous cavity, which is in the inside of the eye. The spots of blood may look like little specks, bugs, or floaters. If a lot of bleeding has occurred, vision can be greatly reduced. If you have diabetes and suddenly see a large number of floaters in an eye, you should notify your eye doctor right away.
Another serious complication of proliferative diabetic retinopathy is neovascular glaucoma. This occurs when abnormal blood vessels grow on the iris and over the drainage system of the eye (the trabecular meshwork). This can lead to extremely elevated eye pressure, pain, redness, and severe vision loss.
How is Proliferative Diabetic Retinopathy treated?
A laser procedure called panretinal photocoagulation is the main treatment for proliferative diabetic retinopathy. In this approach, wide areas of the peripheral retina are treated in a nonspecific pattern of laser spots. This changes the blood vessel circulation in the eye and improves the delivery of oxygen to the retina. Panretinal photocoagulation reduces the amount of VEGF being produced in the eye, which therefore decreases the stimulus for new abnormal blood vessel growth. This treatment is quite extensive and often requires a retrobulbar anesthetic to prevent the laser from being too painful. One or more sessions may be needed to complete this treatment. Often patients have pain for a day or two after treatment, which is usually manageable with non-narcotic drugs. Vision is typically more blurred for a week or two after treatment, and then typically returns to baseline. It is not rare for bleeding to occur inside the eye after treatment because it takes several weeks for the regression of the neovascularization to occur. Some peripheral (side) vision and some night vision may be lost as a consequence of panretinal photocoagulation. Laser treatment for proliferative diabetic retinopathy is one of the most effective treatments in all of medicine. This therapy has saved the vision of millions of patients.
Bevacizumab (Avastin) is a genetically engineered antibody against VEGF that rapidly causes abnormal blood vessels to regress. This medication can be injected inside the vitreous cavity in the office and be very beneficial in the management of certain patients with complications from proliferative diabetic retinopathy. In general, patients with low to moderate risk proliferative diabetic retinopathy do not need this drug, but patients who have very high risk problems can benefit greatly from this treatment.
In some patients, abnormal blood vessels continue to grow and bleed despite good medical and laser treatment. If a patient has a severe vitreous hemorrhage with substantial vision loss, vitrectomy surgery may be required to treat the problem. If the growth of abnormal blood vessels leads to tractional retinal detachment, this is a grave situation, and surgery will be necessary. In general, eyes that are followed closely and treated early for neovascularization stabilize and do well for the long term. A small percentage of patients have such poor blood flow that vision is lost despite excellent treatment.
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