Non-proliferative diabetic retinopathy (NPDR) is a complication of diabetes caused by changes to the blood vessels in the back of the eye. High blood sugars due to diabetes damage the veins, arteries, and capillaries that carry blood throughout the body. This includes the tiny blood vessels in the retina, the light-sensitive nerve layer that lines the back of the eye.
Normal retinal blood vessels are watertight and do not leak. Damaged vessels may develop leaks which allow fluid, blood, and fatty material (exudate) to accumulate within the retina. Accumulation of fluid within the central retina (macula) is calledmacular edema and can lead to reduced vision. Optical Coherence Tomography (OCT) is a test used to detect and measure the extent of macular edema. Fluorescein angiography is a test used to evaluate the circulation of blood through the back of the eye and to identify leaky blood vessels. Leakage in the peripheral retina generally does not affect the vision.
Macular edema is usually treated by retina specialists to try to prevent worsening of vision. Laser is applied to localized leaks in blood vessels while medications such as Avastin (bevacizumab), Lucentis (ranibizumab), and steroids are used to treat leakage that is more widespread or more central in location. The primary goal of treatment is to preserve as much vision as possible. Patients do best when macular edema is treated before vision is affected. Therefore, it is important for diabetics to have their retinas examined regularly.
Proliferative Diabetic Retinopathy
Proliferative diabetic retinopathy (PDR) is a severe complication of diabetes caused by changes to the blood vessels in the back of the eye. In PDR, the retinal vessels are so damaged that they close causing loss of circulation, or ischemia. In response, the retina grows fragile new blood vessels. Unfortunately, these new vessels are abnormal and do not resupply the retina with blood.
Occasionally, these new vessels break causing blood to be released into the clear vitreous gel that fills the eye (vitreous hemorrhage). A small amount of blood will cause dark floaters, while a large bleed might block vision completely.
The abnormal new blood vessels can also cause scar tissue to grow. As the scar tissue contracts, wrinkling and traction on the retina can cause blurred and distorted vision. If the pulling is severe, the retina can detach from the back of the eye causing severe loss of vision.
Laser surgery may be used to shrink the abnormal blood vessels and reduce the risk of bleeding. The body will usually reabsorb small amounts of blood from a vitreous hemorrhage. If the hemorrhage does not clear within a reasonable amount of time or if the retina is wrinkled or detached, an operation called a vitrectomy can be performed. During a vitrectomy, the retina surgeon removes the hemorrhage and the abnormal vessels that cause the bleeding and traction.
Patients with PDR sometimes have no symptoms until it is too late to treat them. The retina may be severely and irreversibly damaged before there is any change in vision. Strict blood sugar control reduces the likelihood of diabetic retinopathy, but it is imperative that patients with diabetes have their retinas examined regularly to detect possible retinal problems while they can be treated. Untreated diabetic retinopathy is the leading cause of blindness among working age Americans.