Ординатура / Офтальмология / Английские материалы / The Eye Book A Complete Guide to Eye Disorders and Health_Cassel, Billig, Randall_2001
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have demonstrated that laser treatments for diabetic retinopathy may also cause a slight loss of visual acuity.
Like any procedure, laser treatment isn’t without its risks—which may include bleeding, increased macular edema, improperly placed laser burns that result in severe vision loss, and increased retinal scarring—and you shouldn’t go into it without a thorough understanding of these. Also, as we’ve said before, because this is your eyesight at stake, you should have the utmost confidence in your surgeon. However, the risks and complications of laser treatment in diabetic retinopathy are rare. For most doctors and patients, they’re far outweighed by the good that these treatments do in preventing retinopathy from getting any worse.
Will laser treatments improve my vision?
Probably not. The main goal of laser treatments for diabetic retinopathy is to slow or halt the progression of this eye disease—in other words, to keep your vision from getting any worse. So you shouldn’t go into this surgery expecting to come out with perfect vision—and if your doctor leads you to believe that this is a possibility, you may want to rethink letting him or her anywhere near your eyes with a power tool. It’s true that a tiny percentage of people do notice a visual improvement after laser treatment for macular edema, but this is the exception, not the rule.
Vitreous hemorrhages often cause annoying symptoms of “cobwebs,” spots, or floaters in the eye, and laser treatments can’t do anything to get rid of them; they’re
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in the jellylike vitreous. As the blood is gradually absorbed, or as it settles, they may become less noticeable, but rarely do they resolve completely. A vitrectomy, if necessary, can remove this blood from the back of the eye and replace the vitreous with water. (This surgical procedure can diminish floaters or spots in the eye.) But again, as with any surgical procedure, a vitrectomy is not without its own set of risks and should not be performed until you have thoroughly weighed the benefits and risks.
How many laser treatments will I need?
It depends on your eyes. Some people may require only one, two, or three treatment sessions per eye to treat macular edema. Others may need ten or twelve treatments over the course of several years to control macular edema and proliferative retinopathy.
Perhaps more important than how many sessions you’ll need—whatever that number may be—is that you and your doctor talk about it thoroughly first, and that you have a reasonable idea of what to expect. It’s easy to get frustrated if you expected a couple of sessions to clear up a problem that turns out to need eight or even a dozen. You’ll also need your fair share of patience, because healing doesn’t happen overnight; your eye will need time to recover—about three months—after each session before your doctor can determine whether you need another one.
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Hypertension
An estimated fifty million Americans have hypertension, or high blood pressure. For most of them, controlling blood pressure is a daily struggle. Over time, hypertension takes its toll throughout the body, particularly in the brain, heart, kidneys, and eyes.
In the eye, hypertension hits the retina hardest, causing tiny arteries there to become even more narrow, impeding blood flow. Although we consider these to be “classic” changes of high blood pressure, they’re often difficult to distinguish from similar “arteriosclerotic” changes that come with normal aging. (Arteriosclerosis, or generalized narrowing of the arteries, is certainly not limited to the eye; it happens in blood vessels throughout the body.) In fact, hypertensive and arteriosclerotic changes can even be seen in the same eye. And hypertension can make arteriosclerosis even worse.
Over a span of years, even relatively mild elevations of blood pressure take their toll on the body’s vasculature, and we can see evidence of this in the eyes. The consequences of skyrocketing blood pressure, especially if it rages uncontrolled for months or even years, can be dramatic and severe: retinal hemorrhages, infarcts (total blockages that prevent blood from reaching tissue) in the nerve fiber layer, and even retinal exudates (fluid leakage into the retina from these blood vessels). One good note, from a diagnostic standpoint, is that these latter changes aren’t subtle and rarely go undetected during an eye exam. They’re almost impossible to miss—which means
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we can work with your internist or family physician to begin treatment for your blood pressure as soon as possible.
Carotid Artery Disease
The carotid arteries are to the brain what the aorta is to the heart: a lifeline—actually, twin lifelines that carry oxygen-rich blood to the head. As they travel upward, these great rivers branch, forming the internal and external carotid arteries. The internal carotid artery is important here because one of its own branches, the ophthalmic artery (again, there are two—one for each eye), supplies blood to each eyeball. The ophthalmic artery, in turn, divides again, becoming the central retinal artery, whose job it is to nourish the inner retina, and the posterior ciliary arteries, which feed the choroid, among other structures. Without life-sustaining blood, these tissues become diseased or die—which is why any ailment affecting the carotid artery can have great ramifications for the eyes.
Atherosclerosis (“hardening of the arteries”) is the most common malady of the carotid arteries. As in the atherosclerosis that leads to heart attacks, this most common cause of artery disease is a historical record of a lifetime’s habits. Every fatty meal, every day or week or decade without exercise, every pack of cigarettes puffed —it’s all here, in the greasy, brittle buildup of cholesterol and fibrous tissue lining the walls of these blood vessels. Over time, atherosclerosis leads to a narrowing of the
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artery’s opening (called the lumen) and a drop in blood flow to the retina and brain. Imagine a garden hose that becomes clogged inside with dirt: the water has trouble getting through. When this happens to blood in the brain, the results can be serious and may include transient ischemic attacks (TIAs), or “mini-strokes”; temporary weakness or loss of sensation on one side of the body; aphasia (difficulty with speech or writing); a loss of vision in one eye (called amaurosis fugax); and severe eye pain (not unlike the intense pain of angina in the heart).
Amaurosis Fugax
Amaurosis fugax is a form of TIA, or “mini-stroke,” that occurs in one eye. An artery is blocked, and tissue is damaged, but the blockage is only fleeting; it clears itself, and blood flow is restored. Amaurosis fugax is the most common symptom of carotid artery disease. You’re driving a car or working in your yard, and all of a sudden your vision becomes dim or dark in one eye—like a “blackout,” a “brownout,” or a gray veil or curtain. Mercifully, this usually lasts only about five to ten minutes, and seldom more than thirty minutes. Vision returns to normal slowly, as if a veil or curtain were being gradually lifted from the eye. There may be another episode within a few days. Note: This event is not usually accompanied by other problems such as dizziness, lightheadedness, headache, trouble talking, or forgetfulness. If you have more prolonged or permanent dysfunction involv-
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ing, for example, your speech or vision or the use of an arm or a leg, this may be due to a stroke.
This temporary vision loss is a warning sign—so don’t ignore it! About one-third of people with untreated TIAs or amaurosis fugax eventually have a stroke. Amaurosis fugax is often caused by small particles—chunks of cholesterol or bits of platelet—that break off from a “hardened” artery and float up to the eye. Usually they become lodged in the small retinal vessels and block blood flow for a few scary minutes before becoming dislodged and moving on downstream. If this doesn’t happen—if they don’t move on—they can cause a branch or central retinal artery occlusion (see chapter 15), a far more severe blockage. (It happens in the eye just as in the brain: a TIA is a small stroke that usually does no lasting damage, but a major stroke can result if there is no return of blood flow—if, in other words, the blockage is not temporary and the damage is more extensive.)
So again, don’t disregard a temporary loss of vision. You will need a thorough medical history and physical examination by your family doctor or internist. It may be that your problem is not caused by carotid artery disease. Several other disorders can also produce temporary vision loss, including giant cell arteritis (see chapter 17), migraine, elevated intraocular pressure, blood-clotting problems, and low blood pressure. In any case, this is nothing to leave “to take care of itself.”
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Ocular Ischemia
Atherosclerosis is a nasty, troublemaking condition in the eye. Amaurosis fugax is one of the problems it causes; ocular ischemia is another. Remember the clogged garden hose described above? In this case the poor hose’s opening becomes increasingly narrowed for prolonged periods, and the garden it’s supposed to water becomes increasingly parched. Here, the hose is the carotid artery, and the garden is the eye itself. (“Ischemic” tissue is parched, as well; it’s starved for blood, oxygen, and nutrients.) Ocular ischemia can be devastating: it can lead not only to loss of vision but even to loss of an eye.
Many patients with ocular ischemia may never realize they’ve got a problem. Here’s another reason for regular eye exams: We can usually detect the problem early enough to treat it. On a routine eye examination, we can see small, scattered hemorrhages (tiny red dots) and other changes in the retina that suggest poor blood circulation in the eye.
Other patients may have a symptom that’s impossible to ignore: the eye’s version of angina. Like angina associated with heart disease, ocular angina is an intense, intermittent pain caused by ischemia. (Think of this pain as the ischemic tissue’s very loud cry for help.) Other people with poor ocular circulation may experience a few minutes of visual difficulty when they go from dark areas into bright light. (However, this may also be due to other ocular problems such as cataracts, age-related
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macular degeneration, or even the need for a new glasses prescription.) (See chapter 15.)
In advanced ocular ischemia, neovascular glaucoma may also develop. This can lead to uncontrollable high eye pressures, causing chronic severe eye pain and discomfort, and result in blindness. In order to preserve eyesight, some people need special treatment: laser photocoagulation or a retinal freezing technique called cryoablation, two techniques for creating retinal scars that can be effective in controlling neovascular glaucoma.
Diagnosis of Carotid Artery Disease
If your eye doctor or family physician suspects that you have carotid artery disease, you’ll need a complete medical history and physical examination. Your carotid arteries will need to be examined specifically, and this may involve several tests. The most widely used of these tests is Doppler ultrasound (also called sonography). Ultrasound, a medical version of the sonar used on submarines (and a technique often used on pregnant women to monitor their unborn babies), can help your doctor check blood flow in the carotid artery.
Ophthalmodynamometry (pronounced op-thal-mo¯ - dy-na- -e-tree), a less commonly used test (it’s being replaced by the more sensitive Doppler technique), can also measure carotid blood flow. It estimates the amount of pressure on the eyeball necessary to block circulation in the retinal arteries. (The less pressure needed to block retinal blood flow, the slower the circulation in the
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carotid artery.) You may require still other tests, such as carotid arteriography in which a doctor injects dye into the blood vessels and takes special pictures as the dye flows through the carotids. (You may have heard of an arteriogram, used to measure heart disease; this is the same technique.) Although more definitive than Doppler studies, “invasive dye studies” also carry more risks, including bleeding, infection, and potential formation of a blood clot. Thus, they’re not the first line of diagnostic testing and are used only in special cases.
Treatment of Carotid Artery Disease
The first step in treating carotid artery disease is to minimize your chances of further damage from poor blood flow. So, how to improve blood flow to your eye? One approach your family physician or internist may recommend is anticoagulation: “thinning” the blood with medications, including aspirin, Coumadin, and ticlopidine or Ticlid. Another approach is mechanical: “cleaning out” the clogged artery, in a procedure such as carotid endarterectomy. It’s the carotid version of a Roto-Rooter technique: a surgeon opens the blocked artery and removes the gunk accumulated on its wall.
Who should get a carotid endarterectomy? This controversial question has been much studied over the last decade, because of the potentially serious complica- tions—such as cerebral and retinal stroke—associated with the procedure. A large, multicentered clinical trial compared the benefits of carotid endarterectomy with the use of antiplatelet medication to decrease clotting
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and improve blood flow. This study found that in patients with symptoms—such as TIAs, including amaurosis fugax—of carotid artery disease and a greater than 70 percent stenosis, or blockage, of the carotid artery, endarterectomy significantly lowered their risk of having a stroke. A more recent study found that endarterectomy was even beneficial in certain patients who hadn’t yet developed these symptoms of carotid disease. Endarterectomy has also been successful in helping people with poor blood flow to the eye as seen in ocular ischemia (see above). In these people, the procedure helped maintain their vision, relieved angina-like eye pain, and even, in severe cases of ocular ischemia, preserved the eyeball. With endarterectomy, patients with ocular ischemia and significant carotid artery disease can regain useful vision if the conditions are caught early enough.
Headaches
Headaches, like fingerprints or snowflakes, are unique. Nobody’s is exactly like anybody else’s—in fact, even in the same person, rarely are two headaches exactly the same.
Headaches can be contained, or localized, to a particular area of the scalp or head; they can be dull or sharp, intermittent or prolonged. They may be accompanied by other symptoms such as nausea, vomiting, dizziness, or “visual phenomena”—seeing wavy lines, or having double vision. Because of the infinite variety here, your doctor isn’t going to be able to help much unless you get spe-