Dry Eye

What is dry eye?
Some people do not produce enough tears to keep the eye comfortable and healthy, this is known as dry eye.

Tears are produced by two 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 irritation or emotions.

Lubricating tears are constantly produced by healthy eyes. The eye produces excessive tears when irritated by a foreign body, dryness, or when crying.

What are the symptoms?

Usual symptoms of dry eye include:

	stinging or burning;
	scratchiness;
	excessive mucus in or around the eyes;
	reduced tolerance to smoke or wind;
	excess tearing;
	difficulty wearing contact lenses.

Excess tearing from dry eye sounds illogical, but if the tears responsible for lubricating do not keep the eye wet enough, the eye becomes irritated. This causes the lacrimal gland to produce a large volume of tears that overwhelm the drainage system, resulting in tear overflow from your eye.What is the tear film?When we blink, a film of tears spreads over the surface of the eye, making it smooth and clear. Without this tear film, good vision would not be possible.

The tear film consists of three layers:

	the oily layer, produced by the meibomian glands, forms the outermost surface of the tear film. Its main purpose is to smooth the surface and reduce evaporation of tears;
	the watery layer is the middle layer. It makes up most of what we think of as tears. Produced by the lacrimal gland, it cleans 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 and helps the eye remain moist. Without the mucus layer, tears would not stick to the eye.

What causes dry eye?
Production of tears normally slows down as we age. Although dry eye occurs in both men and women, women are most often affected, especially after menopause.

Dry eye can also be associated with other problems such as Sjogren's syndrome.

Many common medications, prescription and over-the-counter, can cause dry eye by reducing tear secretion. Be sure to tell your doctor the names of all medications you are taking, especially if you are using diuretics, beta-blockers, antihistamines, sleeping pills, medications for "nerves", or pain relievers. When those medications are necessary, the dry eye condition may have to be tolerated or treated with artificial tears, but be careful, the preservatives in certain eyedrops and artificial tears can irritate the eye. Special preservative-free artificial tears may be better for you to use if that is a problem.

How is dry eye diagnosed?
One test, called the Schirmer tear test, involves placing filter-paper strips under the lower eyelids to measure the rate of tear production. Another uses a diagnostic drop to look for certain patterns of dryness on the eye surface. Still another test is to perform a lactoferrin assay, which is a test of a sample of your tears to determine the lactoferrin level.

How is dry eye treated?
There are various methods of treating dry eye aside from the use of artificial tears. You should discuss your condition with your doctor, who will make a recommendation for you.

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