Dry Eye Syndrome

Tears keep your eyes moist, lubricate the surface of the eye for eyelid closure and guard against infection. They also wash away allergens and protect the eye. Without tears, good vision is impossible. Dry eye syndrome is a group of disorders affecting the film of tears over the eye. In the United States, nearly five million people age 50 or older have dry eye syndrome. Of these, more than three million are women and more than one and a half million are men. In addition, tens of millions of Americans experience less severe symptoms of dry eye.

Dry eye syndrome is one of the most common reasons people visit an eye health professional. It occurs most often in the elderly.

The cause of dry eye syndrome is unknown. External factors may aggravate dry eye symptoms, including conditions common in many workplace environments such as prolonged computer use and exposure to air conditioning, heating, dust and allergens. But dry eye syndrome should not be confused with eye allergies, an even more pervasive problem that affects an estimated 20 percent of the U.S. population. Eye allergies are reactions to substances in the environment that can result in some of the same types of discomforts associated with eye dryness.

When you have dry eye syndrome, either you don't produce enough tears, or you have unstable tears or excessive tear evaporation. Both problems cause your eyes to sting or burn, feel scratchy, become irritated and tear excessively. It most commonly occurs in both eyes, but may affect one eye more than the other. People with dry eyes have difficulty wearing contact lenses. They also may develop mucus in or around their eyes. There can be pain and redness in the eye, a feeling of heavy eyelids or blurred, changing or decreased vision. People with more severe cases of dry eye often are also sensitive to light.

Although eye infections are more common in people with dry eye syndrome, irreversible vision loss from dry eye is rare. More commonly, people with dry eye have fluctuating vision and experience problems with tasks requiring visual concentration such as reading, using a computer and driving. Most people with dry eye find the condition to be an uncomfortable nuisance, with many characteristics of a "chronic pain" type of syndrome.

The tear film on your eyes actually consists of the following three major components:

• Lipid. The outer layer of the tear film is covered by an oily layer produced by meibomian glands in the lower and upper eyelids. This layer smoothes the eye's surface and keeps tears from evaporating too fast and helps them stay on the eye.

• Aqueous. The aqueous component is a watery layer that is produced by the lacrimal glands. This layer makes up most of what we normally consider tears. It nourishes the cornea (the clear tissue of the outer protective layer of the eye that transmits light) and the conjunctiva (a thin, clear layer of tissue that covers the white outer surface of the eye). This tear layer also cleanses the eye and washes away foreign particles or irritants that are wrapped up by the other major component—mucin.

• Mucin. The goblet cells of the conjunctiva, as well as the surface cells of the cornea and the conjunctiva, produce this protective lubricant of tears. It helps spread the watery layer of tears across the eye to keep the eye wet, and it traps and wraps up foreign pathogens and debris so they do not damage the ocular surface.

As we age, the eyes naturally produce fewer tears. However, sometimes, the lipid and mucin layers produced by the eye are so unstable that tears can't remain on the eye long enough to keep it lubricated. Consequently, some people with dry eye may actually have tears running down their cheeks! Dry eye syndrome, also called keratoconjunctivitis sicca or dysfunctional tear syndrome, is the result. In some people, dry eyes result from an imbalance in the composition of their tears or an inability to produce enough tears to keep their eyes sufficiently lubricated. In addition, eyelid problems, environmental factors, certain medications and other causes can lead to dry eyes.

Dry eye occurs most often in older women. Information gathered from the Women's Health Study, a large cohort study in which 25,665 postmenopausal women provided information about the use of hormone replacement therapy (HRT), suggests that those who use HRT, particularly estrogen alone, are at increased risk of dry eye syndrome. A relatively uncommon but often more serious form of the disorder is associated with rheumatoid arthritis or dry mouth and is called Sjögren's syndrome. Sjögren's syndrome is an autoimmune disease that attacks the body's lubricating glands, such as the tear and salivary glands. Allergies can also contribute to eye dryness, causing additional eye discomforts such as itchiness, redness, swelling and wateriness.

Although dry eye syndrome has no cure, its symptoms can be treated. Over-the-counter artificial tears that lubricate the eye are the main treatment. Other treatments include eye ointments, antibiotics (both oral and drops) and avoiding environmental triggers such as hair dryers and rooms with low humidity. And in 2002, the U.S. Food and Drug Administration approved the first prescription treatment for dry eyes, called Restasis (cyclosporine ophthalmic emulsion 0.5%). This treatment increases the body's ability to produce its own natural tears by treating one of the underlying causes of the disease—inflammation.

In cases of moderate to severe dry eye, tears can be conserved by placement of a temporary or permanent punctal plug into the channel at the inner corner of the eyelid where tears drain into the nose and the back of the throat. And in some cases, a surgical procedure to close the tear ducts is in order.

Source: Healthy Woman