Ординатура / Офтальмология / Английские материалы / The Eye Book A Complete Guide to Eye Disorders and Health_Cassel, Billig, Randall_2001
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glasses, one for distance and the other for near vision, on hand.
Myasthenia Gravis
Myasthenia gravis is a neuromuscular disorder, characterized by intervals of weakness and paralysis. It can occur at any age, and it strikes women twice as often as men. Here too, as in thyroid eye disease, the body inexplicably turns on itself, attacking certain muscles—par- ticularly those in the eye, face, throat, and chest—and interfering with their function. An estimated 90 percent of people with this disease eventually develop some eye trouble; in fact, difficulty moving the eye muscles is the most common early symptom. “Droopy” eyelids (a condition called ptosis) and double vision (diplopia) are common, and these symptoms seem to wax and wane over the course of the day. Fatigue makes the symptoms worse.
Although the diagnosis of myasthenia gravis is largely based on someone’s medical history and the physical exam, we now have a chemical test that can confirm its presence. It’s called a Tensilon test, and it works by helping to overcome the antibodies’ effect on the muscles, causing them to function normally again. (Longer-act- ing versions of this drug are also used to treat myasthenia gravis.) Other studies can also be important in helping diagnose myasthenia gravis, such as the acetylcholine receptor antibody test (positive in 70‒93 percent of people with MG), electromyography, and muscle biopsy.
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Acquired Immunodeficiency Syndrome (AIDS)
AIDS is a devastating disease that besieges the body’s immune system, destroying its ability to fight off infection. It targets T-cells, cellular warriors that attack viruses and bacteria—anything the body perceives as an enemy.
AIDS is caused by an insidious virus called HIV (human immunodeficiency virus), and having HIV infection is not the same thing as having AIDS; AIDS represents the late stages of HIV infection. Many people live for a decade or more with HIV before it progresses into AIDS. (About 70 percent of people with HIV develop AIDS within fifteen years.)
When initially infected with HIV, many people experience symptoms of the flu or mononucleosis—such as feeling rundown and having sniffles—for a week or two. Then, nothing. HIV may hibernate for months, years, or even more than a decade before the signs of AIDS begin to appear.
In the eye, the most common manifestation of AIDS is the development of cotton-wool spots in the retina. The problem here is that retinal blood vessels get inflamed, decreasing the blood flow to the nerve fiber layer and damaging the surrounding tissue. Cotton-wool spots usually go away on their own within four to six weeks and rarely affect vision.
Most of the HIV-related problems that do affect vision are indirect, the by-product of a compromised immune system that can no longer stave off infections from op-
Tears and AIDS
AIDS cannot be transmitted by routine social contact with an infected person. You can’t get it from being coughed on, or shaking hands, or using the same computer. As viruses go, HIV’s transmission is pretty limited; it can be passed on only by intimate acts: by unprotected sexual intercourse with someone infected with the virus; by contact with infected blood or tissue (via a shared hypodermic syringe, for example, or a transfusion of tainted blood); or by being born to a mother infected with HIV (and even here, the virus isn’t passed on to all babies of HIV-infected mothers). Although HIV has been found in the body’s secretions—tears, saliva, urine, and bronchial fluids—transmission of HIV from these secretions has not been reported as of this writing.
Having said that: Even though tears are not considered a risk factor, your eye doctor will still (as all doctors should) take precautions to keep the examination and all equipment as sterile as possible. We disinfect tonometers (for intraocular pressure testing) with hydrogen peroxide, alcohol, or a bleach solution. We clean any diagnostic contact lenses that are reused with alcohol-based cleaners and then disinfect them with hydrogen peroxide or heat disinfection to kill HIV. Many of us use disposable contact lenses for diagnostic fitting whenever possible.
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portunistic microorganisms (the “bugs” most of us come into contact with, and fight off, every day). Of these, the most serious threat to vision is CMV, or cytomegalovirus.
CMV attacks the retina in as many as 30 percent of people with AIDS, especially when the number of T-cells in the bloodstream plummets. CMV ravages the retina as it spreads like wildfire, destroying tissue, causing bleeding and retinal detachment. Symptoms of CMV include floating spots or “spider webs,” flashing lights, blind spots, and blurred vision. If you have any of these symptoms, see your eye doctor immediately. However, CMV infection can occur in the eye without any symp- toms—an important reason for all people with HIV to have regular eye examinations.
There are two drugs used to treat CMV: Gancyclovir and Foscarnet. However, these drugs only slow the infection down; they don’t completely eradicate CMV. If CMV is caught early in one eye, these drugs may help to keep the virus from spreading to the other eye.
Other infections common in AIDS are herpes zoster and ocular toxoplasmosis. AIDS complicates the way we treat all of these infections. Usually a drug does only part of the work in fighting a “bug”; the body’s immune system shoulders a large part of the load as well. But in AIDS, because the body’s immune system is failing, normal dosages of drugs are inadequate. Even megadoses— as much as five times the normal potency—don’t always work. Lingering conjunctivitis is also common. Less common is Kaposi’s sarcoma, a noncancerous kind of tumor (which doesn’t threaten vision). This purple-red
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bump may appear anywhere on the body, even on the eyelid or sclera (the “white” of the eye), and can be treated with radiation, laser, or cryosurgery (a freezing technique). If you have AIDS, it’s extremely important— for the sake of your vision—that you have regular eye checkups to catch and treat any eye problems at their earliest signs.
Lyme Disease
The culprit in Lyme disease is a deer tick, a minuscule relation—it’s about as big as the point of a pencil—of the big dog ticks you may have found on your pets.
Many deer ticks are infected with Borrelia burgdorferi, a form of bacteria. The result is Lyme disease—named for Lyme, Connecticut, where this problem was first discovered, although the ticks are found all along the Atlantic coast, from Massachusetts to Maryland, in the upper Midwest in Wisconsin and Minnesota, and along the West Coast in California and Oregon. It’s characterized by distinctive skin lesions, most commonly a round red “bull’s-eye” rash at the site of the tick bite. Its effects can be widespread; early symptoms can include malaise, fatigue, fever, headache, stiff neck, myalgia (muscle soreness), migratory arthralgia (joint soreness), and lymph adenopathy (swollen glands). Note: Lyme disease is not contagious; you can’t get it from someone who has it. You can only get it from being bitten by a tick.
In the eye, most commonly Lyme disease can cause a relatively mild problem, conjunctivitis (see chapter 12).
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More significantly, it can also cause an anterior uveitis (see chapter 14). If not treated, Lyme disease can drag on for months or even years—a terrible thing, when you consider that Lyme disease is easily treated with antibiotics (usually doxycycline or amoxicillin, usually taken for three to four weeks). Similarly, the conjunctivitis can be treated with tetracycline eye drops, along with other medications.
Treatment of the uveitis depends on its severity. A mild case of uveitis may not need any specific treatment; if you’re already taking antibiotics to treat the Lyme disease, the problem should go away as soon as the infection is gone. In some people the disease is localized in the eye. We know this because although their systemic tests for Lyme disease are negative, the borrelia organism is found in the vitreous. If this is the case, a diagnostic and therapeutic vitrectomy may be needed.
19
Coping with Low Vision
with Dena Zorbach, M.S.E.
The American Academy of Ophthalmology defines low vision as what results “if ordinary eyeglasses, contact lenses, or intraocular lens implants don’t give you clear vision.” But that’s a woefully inadequate way of describing one of the greatest challenges—if even that word isn’t too simplistic—to the quality of life.
Low vision means that the simplest, most mundane things you do—reading the newspaper, making coffee, or finding the right bills to pay for a hamburger at a restau- rant—become ordeals. It means that because you can’t see well, life gets unnecessarily complicated and ridiculously frustrating.
It may be some comfort to know that you are not alone. At least twenty million people over age forty have some serious visual impairment. Ninety percent of these people have some vision, often called residual vision. Most of them have what is termed low vision, which can include decreased side vision (peripheral vision), loss of
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color vision, or loss of the ability to adjust to light, contrast, or glare. Again, low vision is defined in the most general terms as the absence of sharp sight even when wearing ordinary glasses, contact lenses, or intraocular lenses.
How Low Vision Impacts Emotions
Loss of vision has a profound effect on the individual, family members, and the community. Next to cancer, older people fear vision loss most. Many people associate low vision with being blind, and many people feel that there is a stigma to being blind. This stigma may be a difficult issue to work through, and it may seem impossible when someone is just beginning the rehabilitation process.
As with any loss, the person with vision loss can be expected to express normal emotions of denial and disbelief, anger, frustration, depression, and fear. The person with vision loss may also experience a loss of mobility, which may make him or her withdraw from social activities and become isolated. And when financial and other personal matters must be handled by others, the resulting loss of autonomy and privacy can be devastating to the person who is used to doing these things for himself or herself.
An overall loss of independence is often a catalyst for reduced self-esteem, productivity, and motivation. Although the period for passing through the emotions of loss varies in length, almost everyone eventually moves
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from saying “I won’t” through believing “I can’t” to learning “I can.” A successful adjustment and rehabilitation of the person experiencing new sight loss will involve family, friends, and significant others. The key to coping with this loss is to accept the reality of the new situation. Once this has happened, the person can begin seeking solutions to life’s new challenges. During this critical period, family and friends need to be encouraging and find ways to help the person become more independent.
Some Devices That May Help
There is life beyond normal reading glasses. If your vision is reduced to a level where regular print is difficult to read with normal reading glasses, there are several “low-vision devices” that can help make books, magazines, newspapers, and mail easier to read. They’re worth considering, and they really can help.
There are five main types of devices: hand-held magnifiers, extra-powerful reading glasses (much stronger than ordinary reading glasses), stand magnifiers, telescopes, and electronic magnifiers. In the future there are likely to be even more helpful devices available, as scientists and engineers collaborate to design and produce rehabilitative devices. One promising new device is the lowvision enhancement system (LVES) developed by Robert Massof and his colleagues at the Wilmer Eye Institute and NASA, which should soon become more widely available.
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Hand-held magnifiers come in a variety of shapes and sizes. One advantage here is that whatever you’re read- ing—a book, a newspaper—can be held at the normal reading distance. You can buy low-power magnifiers, which magnify by about one time (1x) to three times (3x), at most drugstores. Higher-powered models are available at specialized low-vision centers—for help finding one in your area, see “For More Help” at the end of this chapter—or possibly through your eye doctor.
High-powered reading glasses are stronger than your normal reading prescription. One drawback is that because the prescription is so strong, the print must be held very close (or else it looks distorted). For some, this working distance may be uncomfortable, but it does mean that you don’t have to use your hands to hold the vision device, so they’re free to hold the printed page. An adjustable direct-source light, beamed directly at whatever you’re reading, may also help.
Stand magnifiers rest directly on the printed page. They provide a comfortable working distance but a somewhat limited field of view (you can’t scan an entire magazine page at once, for example).
Telescopes can help you see objects farther away. For many people they’re invaluable for seeing bus numbers, street signs, chalkboards, a computer screen, or a baseball game. These can be hand-held, clipped on, or permanently attached to eyeglasses. In thirty states it’s even legal to drive while wearing these telescopes mounted to glasses, called bioptics. Requirements vary: in Maryland, for instance, people with mild visual impairment (20/100