Some people do not produce enough tears or the appropriate quality of tears to keep the eye healthy

and comfortable. This is known as dry eye.

Tears are produced by two different methods. One method produces tears at a slow, steady rate and

is responsible for normal eye lubrication. The other method produces large quantities of tears in response

to eye irritation or emotions.

Tears that lubricate are constantly produced by a healthy eye. Excessive tearing occurs when the eye is

 irritated by a foreign body, dryness or when a person cries.

What Are the Symptoms of Dry Eye?

The usual symptoms include:

	stinging or burning eyes;
	scratchiness;
	stringy mucus in or around the eyes;
	excessive eye irritation from smoke or wind;
	excess tearing;
	difficulty wearing contact lenses.

lubrication do not keep the eye wet enough, the eye becomes irritated. When the eye is irritated, the

lacrimal gland produces a large volume of tears that overwhelm the tear drainage system. These excess

 tears then overflow from your eye.

What Is the Tear Film?

A film of tears, spread over the eye by a blink, makes the surface of the eye smooth and clear.

Without our tear film, good vision would not be possible.

The tear film consists of three layers:

	an oily layer;
	a watery layer;
	a layer of mucus.

The oily layer, produced by the meibomian glands, forms the outermost surface of the tear film.

Its main purpose is to smooth the tear surface and reduce evaporation of tears.

The middle watery layer makes up most of what we ordinarily think of as tears. This layer, produced

by the lacrimal gland, cleanses the eye and washes away foreign particles or irritants.

The inner layer consists of mucus produced by the conjunctiva. Mucus allows the watery layer to

spread evenly over the surface of the eye and helps the eye remain moist. Without mucus, tears

would not stick to the eye.

What Causes Dry Eye?

Tear production normally decreases as we age. Although dry eye can occur in both men and

women at any age, women are most often affected. This is especially true after menopause.

Dry eye also can be associated with other problems. For example, people with dry eyes,

dry mouth and arthritis are said to have Sjogren's syndrome.

A wide variety of common medications — prescription and over-the-counter — can cause

dry eye by reducing tear secretion. Be sure to tell your ophthalmologist the names of all the

medications you are taking, especially if you are using:

	diuretics;
	beta-blockers;
	antihistamines;
	sleeping pills;
	medications for "nerves";
	pain relievers.

tolerated or treated with "artificial tears."

People with dry eye are often more prone to the toxic side effects of eye medications, including

artificial tears. For example, the preservatives in certain eyedrops and artificial tear preparations

can irritate the eye. Special preservative-free artificial tears may be required.

How Is Dry Eye Diagnosed?

An ophthalmologist (Eye M.D.) is usually able to diagnose dry eye by examining the eyes.

Sometimes tests that measure tear production may be necessary. One test, called the Schirmer tear test,

involves placing filter-paper strips under the lower eyelids to measure the rate of tear production under various

conditions. Another uses a diagnostic drop (fluorescein or rose bengal) to look for certain patterns of dryness

on the surface of the eye.

How Is Dry Eye Treated?

Adding Tears
Eyedrops called artificial tears are similar to your own tears. They lubricate the eyes and help maintain moisture.

Artificial tears are available without a prescription. There are many brands on the market, so you may want

to try several to find the one you like best.

Preservative-free eyedrops are available if you are sensitive to the preservatives in artificial tears. If you need

to use artificial tears more than every two hours, preservative-free brands may be better for you.

You can use the tears as often as necessary — once or twice a day or as often as several times an hour.

Conserving the Tears
Conserving your eyes' own tears is another approach to keeping the eyes moist.

Tears drain out of the eye through a small channel into the nose (which is why your nose runs when you cry).

Your ophthalmologist may close these channels either temporarily or permanently. The closure conserves

your own tears and makes artificial tears last longer.

Other Methods
Tears evaporate like any other liquid. You can take steps to prevent evaporation. In winter, when indoor

heat is on, a humidifier or a pan of water on the radiator adds moisture to dry air. Wrap-around glasses

may reduce the drying effect of the wind, but are illegal to wear while driving in some states.

Anything that may cause dryness, such as an overly warm room, hair dryers or wind, should be avoided

by a person with dry eye. Smoking is especially bothersome.

Some people with dry eye complain of "scratchy eyes" when they wake up. This symptom can be treated

by using an artificial tear ointment or thick eyedrops at bedtime. Use the smallest amount of ointment

necessary for comfort, since the ointment can cause your vision to blur.

Dry eye due to a lack of vitamin A in the diet is rare in the United States but is more common in poorer

countries, especially among children. Ointments containing vitamin A can help dry eye if it is caused by

unusual conditions such as Stevens-Johnson syndrome or pemphigoid. Vitamin A supplements do not