If you are reading this, it is likely that you or someone close to you has diabetes, and has been diagnosed with diabetic retinopathy. The following information will hopefully allow you, your family, and your friends to understand diabetic retinopathy. It is important to know how diabetic retinopathy can affect your eyesight, what factors can affect the disease, and what can be done about it.
DIABETIC RETINOPATHY is the most common cause of permanent loss of sight and even blindness in people between ages 25 and 55. However, if a person with diabetes receives proper eye care regularly, and treatment when necessary, diabetic retinopathy rarely causes total blindness.
In diabetic retinopathy, the blood vessels of the retina become abnormal. These blood vessels do not usually leak, but with diabetes, they can develop tiny leaks. These leaks allow fluid or blood to seep into the retina, which then becomes wet and swollen (called thickened in some studies) and cannot work properly. The form of diabetic retinopathy caused by such leakage of the retinal blood vessels is called non-proliferative or background diabetic retinopathy (NPDR).
Another problem with retinal blood vessels in diabetes is that they can close. The area of the retina in which blood vessels have closed then fosters the growth of new abnormal blood vessels, called neovascularization. This can be very bad for the eye because neovascularization can cause bleeding and scar tissue which can result in blindness (total loss of vision). The form of diabetic retinopathy caused by closing of the blood vessels, and in which neovascularization develops, is proliferative diabetic retinopathy (PDR).
Treatment for Diabetic Retinopathy
Laser surgery can be very helpful in the treatment of diabetic retinopathy. A laser beam is high-energy light that turns to heat when it is focused on parts of the retina which are to be treated. With NPDR, the laser heat either seals the leaking blood vessels of the macula, or reduces their leakage and allows the macula to dry. With PDR, the laser destroys the diseased portion of the retina to stop the growth of abnormal new blood vessels.
The major goal of laser surgery is to prevent further loss of vision. Such surgery is not always possible, however. The decision to perform laser surgery depends upon the type of diabetic retinopathy, its severity, and a judgment of how well the disease may respond to laser.
Because diabetes is a condition for which there is currently no cure, the diabetes may continue to damage the retina. Even with laser surgery, patients may continue to lose vision. However, when laser is the right treatment, the chances are good that vision can be stabilized.
If your doctor diagnoses diabetic retinopathy and feels laser surgery might be helpful, a special test called a fluorescein angiogram can be done. For this test, dye (fluorescein) is injected into a vein in your arm, and as dye travels throughout the body, it allows the doctor to take photos of the retinal circulation using a special camera. This is not an x-ray. The photographs taken during this test will show what kinds of changes have occurred in the retina, and provide a type of map which can be used to guide treatment.
Laser surgery for NPDR
The laser is used to stop retinal blood vessels from leaking fluid into the retina in patients with NPDR. Vision does not always improve with laser treatment, but further loss of vision can often be stopped. When the swelling of the retina or the amount of exudate (fluid) in the macula has reached a critical stage (called clinically significant macular edema in some studies), laser should be applied so that vision does not deteriorate further.
There are two types of laser surgery for NPDR: focal, or specific, and grid laser surgery. With focal laser treatment, the specific areas of leakage are found by the fluorescein angiogram, which is then used to guide the laser to attempt to stop the leakage. In some patients, all the leaking points may be properly treated, but they may continue to leak or new leaks may develop. In some cases, additional laser surgery may need to be done frequently to stop new leakage. In severe cases of NPDR - blood vessels appear to leak everywhere in the macula - a scatter of laser treatment in a good pattern is applied across the entire swollen area. Grid laser surgery has a fair chance of drying the macula and holding the vision stable. However, grid surgery usually does not improve vision. Again, your doctor will help you evaluate whether specific (focal) laser surgery, grid laser surgery, or a combination of the two is needed. After such treatment, the patient will often see many small spots caused by laser burns. With time, the spots tend to shrink and fade, and will be less and less bothersome, although they will always be there. Even when laser treatment has successfully sealed the leaking vessels, if the diabetes is not brought under control new areas of leakage frequently appear later, causing more swelling and further loss of vision. A patient who has had laser treatment should continue to check their vision in each eye every day, and tell their doctor immediately if there are any new changes. Again, vision does not usually improve with laser, but if NPDR is discovered early enough, laser may stop further visual loss.
PROLIFERATIVE DIABETIC RETINOPATHY (PDR)
In this form of diabetic disease, retinal blood vessels close off and large areas of the 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 is often diminished. As a result of this loss of nourishing blood flow, the retina responds by developing abnormal blood vessels, called neovascularization.
The development of neovascularization is the retina’s way of coping with closure of its own blood vessels. Many people with diabetes have some closing of retinal blood vessels without neovascularization. However, the problem is that when neovascularization develops, it is never good, and is in fact dangerous to the eye. Neovascularization does not nourish the retina properly, and may cause other problems. One such problem is bleeding into the vitreous cavity (called vitreous hemorrhage). A second problem that occurs when neovascularization develops in the retina is the growth of scar tissue on the retina; this scar tissue can pull the retina off the back of the eye (called a traction retinal detachment). These are both serious problems which can lead to severe loss of vision or even total blindness.
The third problem which can occur is growth of neovascularization on the iris, the colored portion of the eye, rather than just on the retina. When neovascularization grows on the iris (called rubeosis), it may close off the normal flow of fluid out of the eye and cause the pressure in the eye to rise to dangerously high levels, which is called neovascular glaucoma. This can result in visual loss, pain, and even loss of the eye.
It is very important to understand that closing of the retinal blood vessels and growth of neovascularization may occur with no noticeable change in vision. It may be impossible with diabetes and early PDR to know that such change has happened. For this reason, it is essential that every person with diabetes be examined regularly, probably every six to twelve months, by a specialist familiar with diabetic retinopathy. Exams may be more or less frequent depending upon the degree of disease in the retina. These exams should be performed for the lifetime of the diabetic patient. The earlier neovascularization is discovered, the better the chance that laser surgery will save the sight.
Laser surgery for PDR
If retinal neovascularization is detected, laser surgery can often prevent loss of vision. The type of laser surgery done when there is retinal neovascularization is called panretinal laser photocoagulation (PRP).
This type of laser surgery is usually done in two or more separate sessions. The idea is to use the laser to destroy all the dead areas of the retina where the blood vessels have been closed. When these areas are treated with laser, the retina stops manufacturing new blood vessels, and those which were already present tend to decrease or disappear. The side effects of panretinal laser photocoagulation include: decreased night vision; decreased peripheral vision; and possibly a transient decrease in central vision for two to three weeks which normally will get better. Panretinal laser treatment is placed on the side (periphery) of the retina rather than the center, and 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.
When a patient notices a sudden appearance of floaters, spider webs, or spots in front of their eyes, or a sudden blurring of vision, they should immediately contact their eye doctor, as they may have developed a vitreous hemorrhage. It is often helpful for a diabetic who develops a vitreous hemorrhage to remain seated so gravity can help settle the blood to the lower parts of the eye. Once the blood settles, panretinal laser treatment can be performed. Laser surgery cannot make the blood disappear but it causes the neovascularization to shrink, thereby preventing more bleeding into the vitreous. The vitreous hemorrhage usually clears with time, but may take many months to do so.
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 on an outpatient basis, usually with local anesthesia and sedation, although general anesthesia is sometimes used. The blood-filled vitreous gel is removed, and is replaced during the operation with a gas bubble or with a clear fluid 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 vitreous gel. The lack of vitreous gel does not affect functioning 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 considering vitreous surgery.
Traction Retinal Detachment
With PDR, the neovascularization may cause scar tissue to develop. The neovascularization as well as the scar tissue grow across the surface of the retina, and attach firmly to the back surface of the vitreous gel. The gel then pulls on blood vessels and scar tissue, lifting them up. Because the neovascularization and scar tissue are attached to the retina, the retina is also lifted.
When the retina separates from the back of the eye wall, it is called a retinal detachment, and when it is pulled off by the scar tissue, it is called a traction retinal detachment.
Symptoms of a Traction Retinal Detachment
When a retinal detachment occurs, the patient may notice a shadow or a very dark area in the vision. If the retinal detachment extends to the macula, the dark shadow will be directly ahead and vision will be poor. Neovascularization and scar tissue can also cause visual loss because they can wrinkle the retina.
Treatment for a Traction Retinal Detachment
The only way a patient can regain any vision is for the retina to be re-attached and the neovascularization/scar tissue removed from the surface of the retina. This is accomplished by vitrectomy surgery. The surgeon removes the vitreous gel so it will no longer pull on the retina, releasing the traction. The surgeon may remove the scar tissue from the surface of the retina so there is no wrinkling. The detached unwrinkled retina should then flatten and smooth out. The surgeon may perform panretinal laser treatment as well to prevent later development of neovascularization and rubeosis. Laser treatment is also used inside the eye to seal off any tears in the retina. If tears are present, the surgeon may place a gas bubble in the eye to press the retina completely back against the eye wall while the laser surgery takes hold and the eye heals. To help accomplish this, the patient will need to maintain a face-down position for one to two weeks following the procedure. The gas bubble will disappear spontaneously over time.
Closure of macular vessels
If the retinal blood vessels in the macula are closed, the macula stops working. This causes the loss of central or detail vision. Although there is no medical, surgical, or laser treatment for this form of diabetic retinopathy, eyesight may be helped somewhat with the use of special low-vision aids. People with diabetes who have lost central vision must continue to have regular eye examinations because PDR could develop and could damage the remaining peripheral vision.
Preventing Diabetic Retinopathy
A recently completed study known as the DCCT (Diabetic Complication Control Trial) showed that if diabetic patients can maintain their blood sugar at a normal level or below 150 at all time, the complications of diabetes, including serous diabetic retinopathy, can be reduced by as much as 70%. Additionally, control of high cholesterol or hypertension further reduced the risk of diabetic injury to the eye. Smoking cessation may also be beneficial.
The severity of diabetic retinopathy is often related to the length of time a patient has had diabetes. mellitus 20% of type II diabetics (insulin dependent) will develop macular edema within twenty years; 70 - 90% of type I diabetics (non-insulin dependent) will develop some form of diabetic retinopathy within twenty years of diagnosis.
ALL patients with type I diabetes should have their first complete eye examination performed five years after diagnosis. All type II diabetics should be referred to an ophthalmologist immediately for retinal evaluation. A dilated exam of the central and peripheral retina is essential to be sure diabetic retinopathy is not developing.
In the early 1950’s, when diabetic retinopathy began to increase in incidence and no treatment was available, up to 50% of diabetic patients became legally blind due to the disease. Now, with modern techniques in detection and treatment of diabetes as well as of diabetic retinopathy, the risk of severe visual loss in diabetic retinopathy is only 1 - 5%. If you are a diabetic who is able to keep your blood sugar under good control, and you seek regular eye exams as recommended by the American Academy of Ophthalmology as well as the American Diabetic Association, it is highly unlikely that severe visual loss due to diabetic retinopathy will occur.