What are Dry Eyes?
Some people do not produce enough tears to keep the eye wet and comfortable. Stinging, burning, scratchiness, stringy mucus and excess irritation from smoke are the usual symptoms. Dry eyes can make it difficult or impossible to wear contact lenses. Surprisingly, increased tearing may be a symptom of dry eyes. If the basic tear secretion is below normal, excess tears are produced by the lacrimal gland in response to irritation. Even though the eye is basically dry, overflow tearing can occur, masking the dryness which caused the tears in the first place.
What is the Tear Film?
Tears run from our eyes when we cry or when our eyes are irritated. But tears have a much more important everyday function. A film of tears, spread over the eye by a blink, makes the surface of the eye smooth and optically clear. Without our tear film, good vision would not be possible.
The tear film consists of three layers: an oily layer, a watery layer and a layer of mucus.
The outer oily layer of the tear film is produced by small glands at the edge of the eyelid, called meibomain glands. The main purpose of this oily layer is to smooth the tear surface and reduce evaporation of tears.
The middle watery layer, the largest of the three layers, makes up most of what we ordinarily think of as tears. This watery layer is produced by small glands scattered through the conjunctiva, the delicate membrane lining the inside of the eyelid and covering the eyeball and by the major tears gland, the large lacrimal gland. This layer cleanses the eye and washes away foreign particles or irritants. The innermost layer consists of mucus produced by other cells in the conjunctiva. This layer allows the watery layer to spread evenly over the surface of the eye and helps the eye to remain wet. Without mucus, tears would not adhere to the eye.
What are the different kinds of Tears?
There are two kinds of tears: those which lubricate the eye and those which are produced as a response to irritation or emotion. Tears which lubricate the eye are produced around the clock. Excessive tears occur when the eye is irritated by a foreign body or when a person cries.
What causes Dry Eyes?
Tear production normally decreases with age. Although dry eyes can occur in both men and women at any age, women, especially after menopause are most often afflicted
Dry eyes can also be associated with arthritis and accompanied by a dry mouth. People with dry eyes, dry mouth and arthritis are said to have Sjogren's syndrome.
Drugs and medications can also cause dry eyes by reducing tear secretion. Since these medications are often necessary, the dry eye condition may have to be tolerated or treated with "artificial tears."
How are Dry Eyes Diagnosed?
Often an ophthalmologist is able to diagnose dry eyes by simply examining the eyes. Sometimes tests which measure tear production may be necessary. One widely used test, the Schirmer Tear Test, involves placing filter-paper strips under the lower eyelids to measure the rate of tear production under various conditions.
Replacing the Tears
Replacing natural tears with artificial tears is the basis of treatment. Artificial tears are available without a prescription and are used as eye drops to lubricate the eyes and replace the missing moisture. There are many brands of artificial tears on the market and many people try several different brands to find which one suits them best. The tears may be used as often as necessary, once or twice a day, or as often as several times an hour. Solid inserts that gradually release lubricants during the day are also beneficial to some people.
Preventing the evaporation of tears can also prove helpful. In winter, when the heat is turned on, a humidifier or a pan of water on the radiator adds moisture to dry air. Wrap-around glasses (illegal to wear while driving in some states) may cut down evaporation of eye moisture due to wind.
Anything that adds to dryness such as an overly warm room, hair dryers, windy days, or anything that adds an irritant to the air will make a person with dry eyes more uncomfortable. Smoking is especially bothersome.