Many think of diabetes as a disease of insulin. This is, in fact, true and insulin release is abnormal in the diabetic, however, from an eye and kidney standpoint diabetes is mainly a disease of blood vessels. Diabetic retinopathy is retinal damage caused by diabetes. Diabetic retinopathy is usually categorized into two types: background retinopathy (BDR) with changes occurring only within the retina, and proliferative retinopathy (PDR) with changes and problems occurring outside of the retina.
|
Background Diabetic Retinopathy BDR with the white fluffy lesions called cotton wool spots (CWS) , microaneurysms (red dots), and macular edema. |
To understand diabetic retinopathy, you must understand the changes that occur in the retina from this disease. The blood vessels of the retina are much like hoses that you would use in your yard. The vessel itself consists of endothelial cells which make up the wall of the blood vessel surrounded by pericytes which make the blood vessel wall strong and keep the endothelial cells from leaking. In diabetes these cells (pericytes and endothelial cells) have problems with the glue that holds cells together and the cells themselves stop working properly. As diabetic retinopathy (diabetic effects on the retina) progresses pericytes are lost and the endothelial cells' connections are not as strong as a normal vessel. These cells develop outpouchings much like the tire about to blow in a cartoon (microaneurysms), begin to leak and sometimes the vessels completely block off. When a blood vessel closes, the area that blood was going to flow to becomes what we call "ischemic" which means that it is basically having a stroke (no oxygen getting to the tissue). As a result that area of retina may stop working or have difficulty working properly and areas called "cotton wool spots" occur (swollen retina from lack of oxygen). If all the changes that occur in the blood vessels are confined to the retina (loss of cells and leakage) then the retina may thicken in the area of leakage and if this is in the center of vision (macula) we call this clinically significant macular edema (CSME). This thickening of the retina, much like a dry sponge changing to a wet sponge, keeps the nervous tissue from working properly and decreases vision. All of the above changes occur within the retina and are considered "background" diabetic retinopathy (BDR).
When the retina is not getting enough oxygen this can stimulate the growth of new blood vessels and these new vessels usually do not grow within the retina. They will grow out of the retina and along the surface of the vitreous or into the vitreous cavity and are called "neovascularization" (new vessels). Along with neovascularization, scar tissue may form and this scar tissue (fibrovascular proliferation) then grows on the surface of the retina and contracts causing a retinal detachment. Another problem that can occur is that a new blood vessel can break and blood can fill the eye in what we call a vitreous hemorrhage. These later problems might require, in some instances, a vitrectomy to remove the vitreous hemorrhage or scar tissue that has occurred from this type of retinopathy. This is then "proliferative" (new vessels and scar tissue proliferating) diabetic retinopathy (PDR).
|
BDR (NPDR) and PDR BDR changes in macula (center and right side of photo) of patient with marked new vessel proliferation (PDR) of optic nerve at left side of photo. |
Eye care specialists watch carefully for the formation of proliferative retinopathy from background retinopathy and are watching for such things as changes in the veins (venous beading), increases in the number of cotton wool spots indicating that the retina is not getting enough oxygen, widespread changes in the blood vessels called intraretinal microvascular abnormalities (IRMA), and large intraretinal hemorrhages.
Treatment
The treatment of diabetic retinopathy is based on the type of change described above. For macular edema (leakage) the Early Treatment Diabetic Retinopathy Study (ETDRS) showed that there was a great benefit in using laser treatment for treating clinically significant macular edema (CSME) which is defined by varying specific parameters and thickening within certain distances from the center part of vision. There are laser treatments for both focal leakage of fluid and for diffuse leakage of fluid based on which type (or both) of leakage is occurring. More recently the laser treatment pattern has been questioned and the use of steroids in the treatment of the leakage has been raised. The Diabetic Retinopathy Clinical Research Network (DRCR) sponsored by the NIH/NEI was created to look at these questions and future studies on the treatment of diabetic retinopathy. Currently multiple studies are underway by the DRCR which include the use of laser, injection of steroids, and injection of the new anti-VEGF medications. Further we have studied an oral medication (Protein Kinase C) designed to block the progression of diabetic retinopathy in a separate clinical trial.
 |
CSME with exudates Thickening of retina next to the center part of vision with fatty exudates from blood vessel leakage of serum. |
For proliferative diabetic retinopathy the Diabetic Retinopathy Study (DRS) showed that panretinal photocoagulation (PRP) was of great benefit in reducing the rate of severe visual loss in patients with proliferative diabetic retinopathy by 60%. It also reduces the rate of proliferation and progression of disease. Again there are very specific parameters for the use of panretinal photocoagulation.
 |
Panretinal Photocoagulation PRP performed due to new vessel growth and bleeding into the vitreous in a patient with PDR. The macula is at the right edge of the photo. |
Vitrectomy is reserved for very specific problems related to diabetic retinopathy, particularly in the proliferative type of retinopathy. The Diabetic Retinopathy Vitrectomy Study showed the advantages of vitrectomy in patients with severe vitreous hemorrhage, traction retinal detachment, severe progressive fibrovascular proliferation (scar tissue proliferation) and severe neovascularization. It may also be indicated for such things as dense premacular hemorrhage, ghost cell glaucoma, premacular epiretinal membrane traction, anterior hyaloidal fibrovascular proliferation, fibrinoid syndrome, and in very severe cases macular edema.
 |
PDR with Retinal Detachment PDR with fibrovascular (scar tissue) growth along upper major macular vessel and contraction causing a localized "tractional" retinal detachment and marked vision loss. |
One very important study that you need to be aware of is the Diabetic Control and Complications Trial. This excellent study was organized to answer the question "Does intensive treatment with insulin and close monitoring of the glucose lower the risk of complications of diabetes?" In this study 1441 patients with diabetes mellitus were evaluated and there were two treatment regimes: 1. intensive treatment where the patients were given multiple insulin shots, insulin pumps and frequent blood sugar checks and 2. conventional treatment of 1-2 shots of insulin daily with diet and exercise education and infrequent blood sugar testing. Patients in this study were followed for an average of 6.5 years. Of importance in the primary intervention group (no retinopathy at baseline) the risk of developing retinopathy was lowered by 76%. In the secondary intervention group (those patients who already had mild diabetic retinopathy) the risk of progression of retinopathy was lowered by 54% and the development of proliferative diabetic retinopathy was slowed by 47% by good control of the blood sugars. Although all of the complications including eye, kidney, neurologic, cardiovascular, and neuropsychologic were decreased, tight control of the glucose did give a slightly higher possibility of developing hypoglycemia. Weight gain was a problem in the intensive group. The bottom line was the excellent control of the glucose (between 85 and 150) slowed the progression of all the complications of diabetes significantly.
Finally, the recommended timetable for eye examinations of diabetic patients without know diabetic retinopathy is based on age of onset of the disease and the current status of the patient. For patients diagnosed in the first thirty years of life, the first exam should be in the first five years after diagnosis and yearly thereafter. For patients over 30 years of age an exam at diagnosis is recommended with yearly exams thereafter. For pregnant patients, the first eye exam should take place in the first trimester and then at least every three months thereafter based on their physical status. Patients with diabetic eye disease will be followed more closely for progression and possible treatment that could prevent the catastrophic eye complications of this disease.
Disclaimer Stuff: The opinions expressed in this website are those of RVT. Diagnosis and therapy should be based on a thorough examination by and recommendations of a qualified eye provider.