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

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Why don’t my eyes feel dry all the time?

Look around you. For the comfort of your eyes, environment is everything. Temperature and humidity, for instance, both influence tears; sudden changes in either of these can cause dryness.

Indoor heating during the winter, especially the forced-air kind, can significantly dry your eyes, just as it dries your skin. A humidifier, even placing a fish tank in a dry room, can help immensely. (It really is true what they say: “It’s not the heat, it’s the humidity.”) In the summer, air conditioning—which makes the rest of your body so much more comfortable—is designed not only to cool the air but to take excess water out of it as well. And either of these—the loss in humidity or the cool air —can dry your eyes.

Also, the big difference in temperature and humidity that hits us when we go from a heated or air-conditioned house into the seasonal weather takes its toll on the eyes. Until they catch up and adapt to the climate change, our eyes often feel dry as a result.

Spring and fall, the time for relief? No, the time for pollen! If you’re one of the millions of Americans who suffer from pollen allergies, you’re probably way too familiar already with the dry, itching, burning eyes that go along with the sneezing and scratchy throat. A big drawback to oral allergy medications is that they usually make this dryness worse. You may need allergy medications especially intended for eyes; these reduce the swelling and

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itching from allergies but also contain an artificial tear supplement to ease the dryness.

Sometimes I wake up at night with a pain in my eye. What could be causing this?

Two of the most likely suspects are dry eyes and recurrent corneal erosions (see chapter 11). However, another possibility is that you have a recurrent sinus infection. The sinuses surround the eyeball, which means that if they’re inflamed, there can be real discomfort around the eye. See your physician to check for this.

14

The Uvea: Iris, Ciliary Body,

and Choroid

Uvea is the Latin word for “grape,” so it’s a good name for this purple, blood-rich layer of tissue located just inside the eye. In fact, the uvea is sometimes called the eye’s “grape” layer. Lying below the sclera (the “white” of the eye), the uvea is made up of three regions—the iris, ciliary body, and choroid—whose main function is to nourish and maintain the integrity of the eye and its tissues. (For more on the parts of the eye, see chapter 1.) The choroid supplies important nutrients to the retina, while the ciliary body produces aqueous fluid, which is essential to the health of the anterior segment and shape of the eyeball. The iris and ciliary body are also vital in helping the eye see properly.

The two most common problems in the uvea are uveitis and iris nevi.

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Uveitis (Arthritis of the Eye)

Arthritis is an inflammation of the tissues in the joints, right? So how can it be a problem in the eye? Well, in some ways eyes have a lot in common with knees or elbows: both are relatively self-contained, with definite boundaries or walls that create fluid-filled cavities, or spaces, of connective tissue. (In our joints the job of the fluid is to help unyielding surfaces, such as bones and ligaments, move smoothly over each other.)

The eye’s version of arthritis is called uveitis. This is the general term for inflammation of the uveal tissue structures in the eye—the iris, ciliary body, and choroid. Arthritis in the iris specifically is called iritis; in the ciliary body, cyclitis; in the choroid, choroiditis. Uveitis may strike one eye or both. When it does, it can cause redness, throbbing pain, and difficulty with bright light; it may even affect the vision. It can also be “silent” (if it affects only a small area in the back of the eye).

Just as in many cases of arthritis, determining exactly what causes uveitis can be baffling and frustrating. Some cases of uveitis, frankly, stump us; they seem to arise out of thin air. In other people uveitis may be linked to a host of medical problems including headaches, infections, allergies, deafness, numbness or weakness, vitiligo, skin rashes, oral or genital ulcers, bowel problems, joint aches or pains, or difficulty breathing. There’s some speculation that smoking cigarettes and having a poor diet may contribute to the condition.

With uveitis, the first step for the medical professional

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is to take a very careful medical history. Be sure to tell your eye doctor about any other eye problems or general health problems you’re having now or have had in the past (including surgery or trauma). Your doctor may recommend further testing, which may include a chest X- ray and TB test (if a lung problem is suspected), blood tests, stool evaluation, skin tests, or even a spinal tap. You may also need a biopsy (a test in which a small sample of skin or tissue is removed and analyzed).

Even after all these tests, uveitis can be a real challenge to treat; recurrences are common and are frustrating for both the doctor and the patient. Also, just as chronic arthritis can lead to joint-crippling deformities, uveitis can lead to other problems, including glaucoma, cataracts, and swelling in the retina, called macular edema, similar to the macular edema of diabetic retinopathy (see chapter 18).

Fortunately, steroid and nonsteroidal anti-inflamma- tory eye drops—often the first line of treatment—are very effective at treating most forms of uveitis. If the inflammation persists or comes back, your doctor may also inject steroids around your eye or prescribe additional medications including oral steroids, antibiotics, antifungals, antivirals, or even a drug that arrests cell growth (called an antimetabolite).

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Nevi

Iris Nevi

Think of them as freckles in your eye. Like freckles, pigmented nevi on the iris come in all shapes and sizes; even the degree of pigmentation can vary greatly among nevi in the same eye. And, like freckles, they’re almost always benign.

Nevi that are small and unchanging should be routinely checked whenever you get your regular eye exam- ination—every year or two. But if nevi are large, or if there’s a suspicion that they’re growing, then they should be checked at least every few months, because nevi that are on the move—ones that are either growing or changing in shape and color—can cause problems like cataracts and glaucoma.

However, if you have iris nevi, don’t worry. It’s highly unlikely that they’ll ever cause you any trouble. In fact, clinical studies suggest that only 5 percent of even the most suspicious-looking ones ever change—become malignant—within five years. Of course, you don’t want even to take a chance with malignancy, so check the nevi from time to time in your bathroom mirror. Look for any changes in size and color and any changes in the shape of the pupil. You probably won’t find any. But if you do, contact your eye doctor and have it checked out.

Also, your eye doctor may want to make a record of photographs of suspicious iris nevi, to monitor any changes over time.

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Choroidal Nevi and Melanomas (Pigmented Growths under the Retina)

Nevi can also be seen below the retina, in an area of tissue called the vascular choroid. These choroidal nevi are fairly common and can be seen during a routine eye examination. They almost never cause any problems with vision, and they rarely become malignant. It’s estimated that fewer than 15 percent of them ever grow at all over five years. (Here too, as with iris nevi, a photographic record is often an invaluable means of detecting changes and growth.)

Melanomas, malignant pigmented cancers, can also occur in the choroid or ciliary body. They usually develop spontaneously and almost never arise from preexisting choroidal nevi. Like all pigment lesions in the eye, they are slightly more common in people with skin melanoma. However, they are still very rare.

Choroidal and ciliary body melanomas don’t usually produce any early warning symptoms; it’s only as they enlarge that people may experience visual changes or even develop eye inflammation. Because these cancer cells begin to grow under the retina, at first they can be hard to distinguish from benign choroidal nevi or other common retinal changes and growths. When a diagnosis of a choroidal or ciliary body melanoma is made, there are various treatment options to consider. Depending on the size, location, and extent of the tumor, the appropriate treatment may be observation, radiation, or enucleation (removal of the eye).

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As with any medical problem, it’s essential to seek the advice of expert health care professionals with experience in diagnosing and treating your problem.

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sites, including certain blood vessels, the optic nerve, the far edges of the retina, and the macula. But sometimes— as a result of eye or head trauma, or simply of aging— the vitreous jelly can shift and separate from the retina, a condition known as a posterior vitreous detachment, or PVD. (Think of an old house that develops cracks as it settles.)

The repercussions of such shifts vary. Among the most common consequences are what eye doctors think of as “condensations” or “opacifications” in the vitreous, and what patients often describe as “hairs,” “gnats,” or “spiders” in their vision: floaters. Light entering the eye passes around these opacifications in the vitreous and casts a shadow on the retinal photoreceptors; therefore, we see a spot floating. Almost everybody experiences floaters at some point in life. If the shift in the vitreous jelly is associated with traction or rubbing on the retina, patients can also experience quick sparkles of light or lightning: flashes.

Both of these, by themselves, are harmless. A shift in the vitreous alone is no cause for concern. Floaters can go away fairly quickly, or they can last for months to years. Usually, with time, they become less annoying and more tolerable. Flashes due to the rubbing or pulling of the vitreous on the retina are also usually short-lived.

So why worry about the sudden onset of floaters or flashes? If the traction against the retina is significant, the shift of the vitreous can cause the retina to rip slightly.

Such a tear can lead to a retinal detachment. And retinal detachments can lead to permanent loss of vision.