Ординатура / Офтальмология / Английские материалы / The Eye Book A Complete Guide to Eye Disorders and Health_Cassel, Billig, Randall_2001

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is to control your blood sugar. The Diabetes Control and Complications Trial, a national clinical study of the effect of glucose control on diabetic complications, showed that in people with Type I diabetes, intensive insulin therapy delayed the onset and slowed the progression of diabetic retinopathy. (Similar studies on Type II diabetes are under way.) Keeping a tight watch on your blood sugar, with medication or insulin injections and a careful diet, appears to make a major difference in preventing vision problems.

High blood pressure, obesity, infections, and pregnancy are also known to raise someone’s odds of having serious complications from diabetic retinopathy (or from diabetes in general, for that matter). Most of these are within your control: watching your weight and blood pressure, and promptly attending to any infections. Though not always easy, such control is certainly possible to achieve—particularly when the consequences of not doing so can threaten your eyesight.

In addition to taking care of your body, take special care of your eyes. Get a routine eye examination at least once a year (and more often if you’re having vision problems). The American Academy of Ophthalmology has made the following recommendations:

Find an eye doctor who’s very familiar with diabetic eye disease and its many complications. If you have any doubts, seek a second opinion. The stakes—your eyes— are too high for anything less than expert medical care.

Diagnosing Diabetic Retinopathy

As always, an eye examination should begin with a careful history. This should include a discussion of any eye trouble you may be noticing right now: fluctuations in blood sugar often cause intermittent bouts of blurred vision, difficulty with night vision, and trouble reading. (If your diabetes has only recently been diagnosed, you may also experience these problems as your blood sugar is being regulated. Therefore, it’s probably best to wait a couple of months after your blood sugar is under control before you get a new prescription for glasses.)

Your doctor should also learn the specifics of your disease: how long you’ve been known to have diabetes, how well it’s been managed over the years, any other medical problems—such as hypertension or kidney disease—

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you’ve experienced, and anything else that may be important, including any medications you’re currently taking and any allergies you may have. (Also, if the disease runs in your family, be sure to tell your eye doctor if any other relatives have had diabetic retinopathy.)

In the eye examination, your doctor will probably want to check, among other things, your visual acuity with and without your glasses or contacts; to check your distance and reading vision; and to inspect your eyes carefully for signs of glaucoma (which is more common in people with diabetes). Then, using a slit lamp (see chapter 3) to illuminate your eye, your doctor will look for any evidence of external eye infections or cataracts. After this, your doctor will probably dilate your eyes to get a complete view of the retina. Your doctor may also use a direct ophthalmoscope (a hand-held tool that looks like a flashlight) to examine your optic disc, macula, and retinal blood vessels, and an indirect ophthalmoscope (the “coal miner’s lamp” that shines a high-powered light through a special lens) to see the retina’s far edges. (For more on what to expect from a detailed eye exam, see chapter 3.)

Sometimes other techniques are needed to measure someone’s degree of retinopathy—particularly when macular edema is suspected but not obvious, or if the edema is so extensive that it’s tough to distinguish the exact areas of leakage. If this is the case, you may also need a test called a fluorescein dye study, which involves intravenous injection of a dye into the blood vessels. Your doctor will take a timed series of photographs of

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your retina, tracing the dye’s progress as it enters the blood vessels, passes through them, and exits the eye. If you have macular edema, this study will show your doctor where the trouble spots are by highlighting the leaks. This study is painless, with few side effects—the most common one being that the orange dye temporarily gives the skin a mildly jaundiced tint and turns your urine a startling shade of yellow for about twelve hours. Some people also feel a brief twinge of nausea at the time of injection, as the dye rapidly circulates through the body.

Treating Diabetic Retinopathy

The good news is that, thanks in large part to extensive research efforts directed by the National Eye Institute, we’ve made great strides in treating this complicated problem over the last thirty years—so much progress, in fact, that today most people with diabetic retinopathy don’t suffer severe visual impairment from it.

Treating Macular Edema

The breakthrough weapon against macular edema is the argon laser, and the treatment is called photocoagulation. Basically, the doctor uses a laser and, guided by the results of the fluorescein angiogram, “spot-welds” the seeping blood vessels in the macula. If the leaks are small, the laser is applied directly; if leakage is widespread, the laser is used in a grid pattern, like a patchwork quilt, over a broader area. An average treatment session will require between fifty and one hundred pinpoint-sized laser “spots.”

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Note: Your doctor will probably tell you this, but it’s worth repeating just the same: all laser treatments for diabetic retinopathy, macular edema, or proliferative disease are done to keep vision from getting worse, not to make it better. So don’t be disappointed if a laser treatment for diabetic retinopathy does not improve your vision.

Another important point: laser treatment doesn’t absolutely guarantee that someone with macular edema won’t suffer significant visual impairment, but it does lower the odds considerably. In a large clinical trial, called the Early Treatment Diabetic Retinopathy Study, sponsored by the National Eye Institute, patients who underwent laser treatment had significantly less visual impairment than those who received no treatment (14 percent versus 32 percent at three years).

The procedure is tricky. Because the area in question, the macula, is so small that any false step can have a devastating and permanent effect on someone’s eyesight. Most of that burden rests on your doctor, who must know exactly where to place the laser. But part of the burden is yours. Your job, throughout the procedure, is to sit completely still—without moving your body or eye. (Special anesthesia can be given to help keep your eye from moving; see below.) The treatment session may take anywhere from fifteen to forty-five minutes. Then, when it’s over, you can immediately return to your normal activities; usually there aren’t any postoperative restrictions.

The laser treatment is performed as a same-day pro-

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cedure, usually at your doctor’s office or in an eye clinic; there are no preoperative testing requirements. Immediately before the procedure, you’ll be given dilating eye drops to enlarge your pupil and give your surgeon a clear view of the retina. Since the procedure is performed using a special contact lens on the eye, you’ll also be given anesthetic drops to numb your cornea. Some people also receive an injection of local anesthesia—like the novocaine you get in the dentist’s office—near and behind the eyeball to prevent discomfort and minimize eye movement.

The actual laser treatment is delivered, with highpowered magnification, through a slit lamp biomicroscope (like the kind used in a routine eye examination). With each laser “spot,” or burn, you’ll probably notice a click and a bright flash. Although there’s usually no pain, some patients do feel a little discomfort.

Afterward you may experience a mild headache and some temporary blurring of vision; both of these should clear up gradually over the next twenty-four hours. (If symptoms persist longer than a day, call your eye surgeon.) A lightweight patch, worn for the first day or so afterward, can help by decreasing light sensitivity and relieving the blurring. You may also be given some steroid eye drops to ease any postoperative swelling. Note: Although you can resume your normal activities—reading, exercising, working, and driving—right away, it’s a good idea to have someone drive you home; you won’t feel “100 percent” for about a day. (For more on side effects, see below.)

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It generally takes about three months for the laser treatment to have an effect on macular edema. If by the end of that time your edema has not substantially subsided (and this is often the case after the first go-around), then you may need a “touch-up” session, or several (it’s not uncommon for someone to need three or four separate treatments), until the fluid is judged to be minimal.

As we’ve discussed, macular edema can be especially difficult to treat in people with poorly controlled diabetes, people with hypertension or fluctuating blood sugars, and people who are pregnant or who have kidney problems or infections such as bacterial foot ulcers. Whatever you can do to improve the rest of your health will certainly boost your odds of having successful treatment.

Treating Proliferative Diabetic Retinopathy

Many years ago eye doctors noted that people with diabetes who had large areas of retinal scarring—from such problems as infection or trauma—seemed less likely to develop proliferative diabetic retinopathy. This led investigators to create artificial scars on the retina, to see if this had the same protective effect.

It did. In the late 1970s, after encouraging results from earlier studies, the National Eye Institute’s national Diabetic Retinopathy Study confirmed the theory: somehow, scarring—done with argon lasers—indeed slows or stops out-of-control blood vessel growth in proliferative diabetic retinopathy. The study’s results were striking. Four years after undergoing argon laser treatment, patients were less than half as likely to develop severe vision

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loss as those who hadn’t received this treatment. Note: Again, as with macular edema, the laser is not a cure-all for proliferative diabetic retinopathy; it’s not guaranteed to prevent severe vision loss, but it does significantly lower the odds.

Laser treatment for proliferative diabetic retinopathy is more extensive than the “spot-welding” used for macular edema (although many features of the procedure, including anesthesia, are the same; see above). The technique here is called panretinal photocoagulation; instead of fifty to one hundred laser “spots,” or burns, it may involve eight hundred to two thousand pinpoint-sized burns and may take two or three sessions to finish.

The idea, basically, is to scar most of the retinal tissue. Nobody quite understands why this helps slow rampant growth of new blood vessels. It may be that the scarring decreases the amount of angiogenic factor (the retina’s “chemical cry for help” mentioned earlier) released by the retina; or that it improves blood flow in the mature vessels; or that it lowers the retina’s need for oxygen (and thereby reduces its need for new blood vessels). Whatever the reason for its effect, this treatment has been tremendously helpful for people faced with proliferative disease. (For more on the side effects of laser treatments, see below.)

Treating Vitreous Hemorrhage and Tractional

Retinal Detachments

As discussed above, the fragile offshoot blood vessels of proliferative diabetic retinopathy bleed at the slight-

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est provocation. When they spill blood in the retina and into the vitreous cavity—producing a vitreous hemor- rhage—they can cause scarring on the surface of the retina and in the vitreous jelly. Unlike the deliberate scarring done with the laser to combat proliferative retinopathy, this scarring is dangerous for vision. Over time it gradually contracts, as all scar tissue does, and takes the retina along with it, causing it to separate from the back of the eye. This is a tractional retinal detachment (see chapter 15), a serious process that can severely impair vision and even lead to blindness.

However, we now have a successful way to treat vitreous hemorrhage: a procedure called vitrectomy. Using specially designed instruments—scissors, picks, and tiny lights for guidance—retinal surgeons can now remove the vitreous hemorrhage from the back of the eye, carefully stripping away scar tissue and relieving the pulling on the retina. The success of this surgery was investigated and confirmed more than a decade ago by the National Eye Institute’s national Diabetic Retinopathy Vitrectomy Study. This large study particularly showed the benefit of early vitrectomy for a severe vitreous hemorrhage in a person with Type I diabetes, but not in a person with Type II. Laser photocoagulation or cryotherapy of the retina may also be used during vitrectomy surgery to treat any underlying proliferative retinopathy.

Coping with Diabetic Retinopathy

Diabetes takes its toll on the whole body—including your emotional well-being, which can have a great in-

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fluence on the course of your disease. Depression and anxiety are very common in diabetes, and understandably so—particularly in people who are newly diagnosed or who have just been told they have diabetic retinopathy. Sometimes emotional problems and difficulty cop- ing—which may be triggered by having any chronic dis- ease—can sap patients’ motivation and jeopardize their ability to control the diabetes. If there’s a possibility that your emotional reactions may be interfering with the management of your illness, don’t hesitate to seek professional help. Also, your doctor may be able to recommend local support groups. It can help tremendously simply to talk about what you’re going through with people who are experiencing the same kinds of problems.

Some Questions You May Have about Laser Treatments for Diabetic Retinopathy

Does laser treatment have any side effects?

Usually only minor, temporary ones, such as mild swelling, blurred vision, and light sensitivity. However, laser treatments for macular edema, if placed close to the center of the macula or in a pattern to cause a dense scar, sometimes result in small areas of “blind spots,” which are usually most noticeable when you’re reading. Panretinal treatment for proliferative diabetic retinopathy, because it’s performed mainly in the peripheral retina, can make it more difficult to see at night and may slightly reduce your peripheral and color vision. Clinical studies