Diabetic Retinopathy San Antonio
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What is diabetic retinopathy?
In diabetic retinopathy the blood vessels of the retina become abnormal and cause the problems that diabetic patients have with their eyesight. Normally, the blood vessels in the retina do not leak. But with diabetes, the retinal blood vessels can develop tiny leaks. These leaks cause fluid or blood to seep into the retina. The retina then becomes wet and swollen and cannot work properly. The form of diabetic retinopathy caused by leakage of the retinal blood vessels is called background diabetic retinopathy (BDR).
Another problem with the retinal blood vessels in diabetes is that they can close. The retinal tissue, which depends on those vessels for nutrition, will no longer work properly. The areas of the retina in which the blood vessels have closed then foster the growth of abnormal new blood vessels that can be very bad for the eye because they can cause bleeding and scar tissue that can result in a total loss of vision. The form of diabetic retinopathy caused by closure of the blood vessels and win which abnormal new blood vessels grow is call proliferative diabetic retinopathy (PDR).
Background Diabetic Retinopathy
 In diabetes, the retinal blood vessels can develop tiny leaks. Blood and fluid seep from the retinal blood vessels, and fatty material, called exudate, deposits in the retina. This causes swelling of the retina, and it is called nonproliferative diabetic retinopathy (NPDR). When this occurs in the central part of the retina (the macula), vision will be reduced or blurred. Leakage elsewhere in the retina will usually have no effect on vision.
A patient with a wet, swollen macula, or with exudate in the macula, will experience some loss of vision, including blurring, distortion, or darkening. If one eye is affected, the other eye is frequently affected also, though the problem may not be equally severe in both eyes. If the diabetic retinopathy has affected each macula severely, central vision may be lost from each eye. But even if the ability to see detail has been lost from both eyes, the person with severe NPDR will usually be able to get along fairly well by learning to use the area just outside of the macula to see some detail. This ability to look slightly off center usually improves with time, though the eyesight will never be as good as it was before the macula was damaged by the leakage of blood vessels. So patients who have NPDR will usually be able to see well enough to take care of themselves and continue those activities that do not require detail vision.
Early Diagnosis of Nonproliferative Diabetic Retinopathy
It is important that patients be aware of what they are seeing with each eye. If a patient can detect a problem with vision very early, the chance of saving eyesight with laser surgery is much greater. Once the macula has been damaged, laser surgery is generally not as helpful. For this reason, everyone should test the vision in each eye, separately, each day.
One way to test vision in order to detect even small changes when they first appear is to use the Amsler grid. Follow these instructions:
- Wear your reading glasses and hold the Amsler grid at a normal reading distance.
- Cover one eye.
- Look at the center dot and keep looking at it at all times.
- While looking directly at the center, be sure that all the lines are straight and all the small squares are the same size.
- If you should notice any changes on the grid such as distortion, blur, discoloration, or other abnormality, and it stays that way for a few days, call and see your eye doctor right away.
- Be sure to test the other eye in the same manner.
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Laser Surgery for Diabetic Retinopathy
The laser is used to stop abnormal retinal blood vessels from leaking fluid into the retina. Vision does not usually improve with laser, but laser can frequently stop further loss of vision. When the swelling of the retina or amount of exudate in the macula has reached a critical stage, laser should be done so that vision does not deteriorate further. Your own doctor can help you evaluate your chances with laser and discuss the options with you.
There are two types of laser surgery for NPDR: Focal (or specific) surgery and Grid surgery. With focal laser surgery, the specific leaking spots in the retina are found by a fluorescein angiogram, which is then used as a guide for the laser in an attempt to stop the leakage. In some patients, all of the leaking spots may be properly treated. In some patients, all of the leaking spots may be properly treated, but they may continue to leak, or new ones may develop. In such cases, further leakage causes more swelling and worsening of vision. Additional laser surgery frequently needs to be done in order to stop new leakage, but again, the vision is not likely to improve. In other situations, further laser surgery is not helpful and should not be done.
In some cases of NPDR, blood vessels appear to be leaking everywhere in the macula and not just in a few specific areas. In such cases, a scatter of laser in a grid pattern is placed across the entire swollen macular area. Grid laser surgery has a fair chance of drying the macula and holding vision stable. Grid surgery, however, infrequently improves vision. Again your doctor will help you evaluate whether specific (focal) or grid surgery, or a combination of the two, is best.
Grid Laser of Diffuse Diabetic Macular Edema
After the laser surgery, the patient will often see the many small spots caused by laser burns. With time, the spots tend to shrink and fade, and the patient will be less bothered by them, though they will always be there.
Even when laser surgery has successfully sealed the leaking vessels, new areas of leakage frequently appear later, causing more swelling and more loss of vision. The patient who is treated with laser should continue to check the vision in each eye daily and tell the doctor immediately if there are new changes, such as a return of distortion or blurriness. Vision does not usually improve with laser surgery, but if NPDR is discovered early enough, laser surgery may stop further loss.
Proliferative Diabetic Retinopathy
In PDR, retinal blood vessels close off, and large areas of retina lose their source of nutrition. When this happens, peripheral or side vision is usually reduced, and the patient's ability to see at night and to adjust from light to dark is often diminished.
As a result of this loss of nourishing blood flow, the retina responds by developing new blood vessels that are abnormal and are called neovascularization. The development of neovascularization is the retina's method of coping with the closing of its own blood vessels and the loss of nourishment. Many people with diabetes have some closing of retinal blood vessels without ever developing neovascularization. But the problem is that when neovascularization develops, it is never always a problem. It is, in fact, dangerous to the eye. Neovascularization does not nourish the retina properly, and it may cause other problems. One problem is bleeding into the vitreous cavity (called vitreous hemorrhage). A second problem that occurs when neovascularization develops is the growth of scar tissue on the retina; the scar tissue can pull the retina off the back wall of the eye (called a traction retinal detachment). Either of these serious problems, vitreous hemorrhage or traction retinal detachment, can lead to severe loss of vision or even total blindness.
A third problem that can occur is when neovascularization grows on the iris, the colored part of the eye, rather than just on the retina. When neovascularization grows on the iris (called rubeosis), it may close off normal flow of fluid out of the eye and cause the pressure in the eye to rise to dangerously high levels. The high pressure (called neovascular glaucoma) can cause permanent changes, resulting in visual loss, pain, even loss of the eye.
It is very important to understand that the closing of retinal blood vessels and the development and growth of neovascularization may occur without any noticeable change of vision. So, it may be impossible for the person with diabetes and early PDR to know that such changes are occurring. For this reason, it is essential that every person with diabetes be examined regularly by a specialist who is familiar with diagnosing diabetic retinopathy. Such examinations should occur regularly--probably every six to twelve months, or more or less frequently--for the lifetime of the person with diabetes. The earlier neovascularization is discovered, the better the chance that laser surgery will save vision. The later neovascularization is discovered, the greater the chance for blindness.
All People with diabetes should be examined regularly to be sure that neovascularization is not developing. When neovascularization does develop, if the amount is not severe, laser surgery is not necessary as long as the patient is examined regularly.
If the amount of neovascularization is great, laser surgery can often prevent loss of vision. The type of laser surgery that is done when there is a lot of neovascularization is called pan retinal laser photocoagulation. This type of laser surgery is usually done in two or more separate sessions. The idea is to use the laser to destroy all of the dead areas of retina where the blood vessels have been closed. When these areas are treated with the laser, the retina stops manufacturing new blood vessels, and those that are already present tend to decrease or disappear.
Pan retinal Photocoagulation
There are side effects of pan retinal laser photocoagulation and, for this reason, this surgery is not done when only a small amount of neovascularization is present. It is important to remember, however, that when the amount is great enough to warrant laser surgery, the longer the eye remains untreated the more likely vision will be lost and blindness will occur. The earlier severe neovascularization is discovered and the eye is treated with laser the more likely blindness can be prevented. If you have developed neovascularization, your doctor will advise you about when pan retinal laser photocoagulation should be done.
Pan retinal laser photocoagulation does not improve vision, however, it is the best possible means of holding vision stable to prevent further loss. After laser surgery, patients may still have reduced vision or may continue to lose more vision. But if pan retinal laser photocoagulation is indicated, the chances are that it will prevent severe loss of vision.
Pan retinal laser photocoagulation is placed on the side (periphery) of the retina, not on the center, and side (peripheral) vision will definitely be diminished to some extent. These side areas are sacrificed in order to save as much of the central vision as possible and to save the eye itself. Night vision will also be diminished. After laser, blurred vision is very common. Usually, this blur goes away, but in a small number of patients, some blur will continue forever.
Because diabetic retinopathy can occur at any time, the patient who is treated with laser for either NPDR or PDR should have regular retinal examinations by an eye specialist.
Vitreous Hemorrhage
 Because vitreous hemorrhage is not necessarily associated with any specific activity (although it can be associated with strenuous physical activity), people with diabetes are encouraged to lead a normal life and not restrict their physical activities for the sake of their eyes. There may be exceptions to this general rule, and your doctor will help advise you. When a person does notice the sudden appearance of floaters, spider webs, spots in front of the eye, or blurred vision, they should immediately call their eye doctor.
Treatment
It is often helpful for someone with diabetes who develops a vitreous hemorrhage to remain in a sitting position so that gravity can help settle the blood to the lower parts of vitreous cavity. Once the blood settles, pan retinal laser photocoagulation can be done. Laser surgery cannot make the blood disappear, but it can cause the neovascularization that bled to shrink and thereby prevent more bleeding into the vitreous. The vitreous hemorrhage that is present usually disappears with time but can take many months to clear.
If there is so much vitreous hemorrhage that laser surgery is not possible, or if the blood does not disappear on its own, it can be removed with an operation called a vitrectomy.
Vitrectomy surgery is done in the hospital, under general or local anesthesia. The blood-filled vitreous gel is removed. It is replaced during the operation with a gas bubble or a clear fluid that is compatible with the eye. Over time, the gas bubble or fluid is absorbed by the eye and is replaced by the eye's own fluid, although the eye does not replace the gel itself. The lack of vitreous gel does not affect the function of the eye. If the blood in the vitreous does not go away on its own, your doctor will advise you as to how long you should wait before vitrectomy surgery is considered.
Traction Retinal Detachment
 In PDR, the neovascularization may cause scar tissue to develop. The neovascularization and the scar tissue grow along the surface of the retina and attach firmly to the back surface of the vitreous gel. The vitreous gel pulls on the blood vessels and scar tissue and lifts them up. Because the neovascularization and scar tissue are attached to the retina, the retina is also lifted up. When the retina separates from the back surface of the eye, it is called a retinal detachment. Because the retina is pulled off, it is called a traction retinal detachment. The scar tissue can also tear the retina and cause a retinal detachment.
When a retinal detachment occurs, the patient may notice a shadow or very large dark area in the vision. When the retinal detachment extends to the macula, the dark shadow will be straight ahead and vision may be poor. The neovascularization and scar tissue also can cause visual loss because they can wrinkle the retina.
The only way the patient can regain any vision is for the retina to be reattached and the neovascularization and scar tissue to be removed from the surface of the retina. This is accomplished by vitrectomy surgery. The surgeon removes the vitreous gel from the eye so that it stops pulling on the retina; the traction is released. The surgeon may remove the scar tissue from the surface of the retina so that there is no wrinkling of the retina. The detached and wrinkled retina should flatten and smooth out. The surgeon may also perform pan retinal laser photocoagulation to prevent further development of neovascularization and rubeosis.
The surgeon also uses laser inside the eye to seal any tears of the retina. If there are tears in the retina, the surgeon may place a large gas bubble in the eye to press the retina completely against the back wall of the eye while the laser surgery takes hold. In order to accomplish this, you may be asked to position your head facing down or up for a week following the surgery. In time, the gas bubble will disappear and be replaced by the eye's own fluid.
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