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The most frequent patient complaint to ophthalmologists and optometrists is dry eyes, known technically as aqueous insufficiency. About 33 million Americans in all age groups experience varying degrees of dry eye symptoms. 1 The symptoms may include dryness, grittiness, irritation, burning and even the seeming contradiction, of excessive tearing or watering.

Any condition that reduces the production, alters the composition or impedes the distribution of the tear film may result in dry eyes. Like most eye conditions, dry eye syndrome is often related to health conditions in the rest of the body. It is commonly associated with dryness of other mucous membranes, interior body surfaces such as joints and brittle nails. It also can be a sign of digestive imbalances or of more serious systemic autoimmune diseases, such as rheumatoid arthritis, Sjögren's syndrome or lupus erythematosus.

These diseases trigger an immune response, generating lymphocytes that slowly destroy the cells responsible for tear production and secretion. As a result, tear volume decreases, cells in the conjunctiva decrease and corneal cells can be lost, creating dry spots. In Sjögren's syndrome, for instance, the entire lacrimal gland responsible for 90 percent of tear production may be destroyed by the invasion of inflammatory lymphocytes.

Who Gets Dry Eyes?

Dry eyes are mostly a health problem for women, and seems to be a result of fluctuations in hormone levels, particularly estrogen and androgens. Pregnant women, women who use birth control pills and postmenopausal women on hormone replacement therapy frequently report dry eyes.

Dry eyes in postmenopausal women also can be a sign of Sjögren's syndrome, also known as Sicca syndrome. Sjögren's syndrome, which afflicts four million American women, is considered the most commonly misdiagnosed of all health conditions in women over the age of 40. In Sjögren's syndrome, dry eyes are accompanied by dryness in other parts of the body: dry mouth, dry joints (arthritis), sore throat, dry skin, dry cracked lips, dry scalp (dandruff) and brittle nails. This pattern of symptoms is produced by an autoimmune process in which antibodies attack fluid-secreting cells. Fatigue, Raynaud's disease and dental caries also are often present.

Dry eyes also can be an isolated problem. Older people naturally have drier

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eyes, because, as we get older, our eyes produce on average 40 percent less lubrication. Free radicals are partly to blame; they take their toll over time, damaging body tissues and increasing the prevalence of dry eye symptoms. Some people lack a sufficient volume of tears, or their tears might have the wrong composition. In addition, a problem with the eyelid can prevent the tears from distributing over the eyes properly.

Long-term contact lens use also can contribute to dry eyes, because, over time, contact lenses can reduce corneal sensitivity. The sensitivity of the cornea and the entire ocular surface determines how many tears the lacrimal gland will secrete. The less sensitive the cornea, the fewer tears you will have.

Forty percent of dry eye patients are smokers, so tobacco smoke, environmental allergens, air conditioning and wind may also cause dry eyes. Many medications trigger dry eye, most commonly antihistamines, codeine, decongestants, diuretics, morphine, oral contraceptives and even eye drops such as Visine and Murine.

WHAT ARE TEARS?

By understanding tears and tear production, we can find healthy solutions for many dry eye sufferers.

Tears are the clear, salty liquid that lubricates our eyes. There are actually three layers that keep the front surface of the eye comfortably lubricated and optically clear.

The outermost is an oily layer, secreted by the Meibomian glands in the eyelids, that prevents the tears from evaporating and the eyelids from sticking together.

The middle and thickest layer is the watery or aqueous layer, which makes up about 90 percent of the tear film. This layer is secreted by the lacrimal glands, which formulate its secretions in small sac-like cells called acinar cells. Any damage to acinar cells reduces the lacrimal gland's ability to produce moisture. Many of the critical functions of the tear film providing nutrients, removing debris, fighting bacteria and generally lubricating the eye occur at this level.

The innermost layer of the tear film, which binds the tears to the surface of the eye by making the eye tissue ''wettable,'' is the mucous

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layer. This is secreted directly from the conjunctival surface onto the white of the eye by the goblet cells. A breakdown in any one of these layers can cause dry eyes.

Treating Dry Eyes

Standard medical treatment for dry eyes includes two options: artificial tear preparations in the form of eye drops or punctal occlusion.

Artificial Tears

Although many people find temporary relief with artificial tear preparations, they merely palliate the symptoms. Worse, the preservatives in many of these products can aggravate the condition. In fact, they can even kill corneal cells. Eye drops called vasoconstrictors, that promise to "get the red out," will reduce circulation in the eye, decrease production of the tear film, and worse, eventually make your eyes even drier.

Always use eye drops without preservatives. These have been shown to enhance corneal healing and improve dry eye problems. 2 A good brand is Thera Tears, which has been shown to aid in the healing of dry eyes after eight weeks of treatment. (Use two to six drops in each eye four times a day, at 8 a.m., noon, 3 p.m. and 6 p.m.; see Resources.)

Another good eye drop solution is Viva-Drops, which contains antioxidants and vitamin A. Patients have reported 90 percent improvement in several studies. Use two or three times a day for 30 days.

HOW TO USE EYE DROPS

Eye drops can be difficult to use, particularly for children and the elderly. Few doctors instruct their patients in using eye drops, so up to 80 percent of people have difficulty with this initially. Even with practice, 49 percent continue to have poor aim.3

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Using eye drops is actually simple if you pull down the lower lid and let the eye drops fall into the lower lid rather than directly onto the cornea. (See illustration.)

If you can't seem to keep your eyes open while the drops fall into the eyes, drop them into the inner corner of the closed lids and the drop will enter the eyes on opening.

Blinking and tearing following use of eye drops can dilute them to less than one percent of their original concentration in just a few minutes. Therefore, don't blink, but rather close the eyes for up to two minutes to give the drops a chance to work. 4 Pinching gently at the bridge of the nose to prevent drainage through the tear ducts also will increase the effectiveness of the eye drops by 65 percent.5 Other tips:

Wash your hands before using eye drops and keep the bottle in a clean place.

If the eye drops sting your eyes, keep the eye drops refrigerated. The cold will lessen the sting.

Be sure to keep your eye drops separate from any similar looking bottles. To prevent contamination, be careful not to touch the dropper with anything, including fingers or the eye itself. If there is a dirty ring between the cap and the lid, the eye drops probably are contaminated and should be discarded.