Q: What is “dry eye syndrome”? Don’t everybody’s eyes get dry from time to time?

A: We have all experienced the (usually temporary) symptoms of dry eyes at one time or another, especially if we work at a computer or have been exposed to too much smoke, wind or sun. But dry eye syndrome is a serious, chronic condition many people experience, where not enough tears are produced to keep the eye comfortable.

Over the course of a day, we blink nearly 12,000 times. But for people with dry eye syndrome, each blink can be irritating and even downright painful.

Two types of tears

Oddly enough, one symptom of dry eyes is an excessive production of tears. This happens because there are actually two types of tears at work in your eye. The first are called reflex tears, which are triggered by irritation, such as getting sand in your eyes or slicing an onion, or by emotions that cause tears.

The second type is called the basic tearfilm, which lubricates the surface of the eye during blinking and covers and protects the eyeball when your eyes are functioning normally. It is this second type of tears that causes problems. In people with dry eye, this tearfilm becomes unstable, allowing dry spots to form on the cornea (the central portion of your eyeball). These dry spots cause irritation every time the eyelid passes over the cornea, which in turn causes reflex tears to flow as the eye tries to lubricate itself and deal with the irritation.

Causes and culprits

There are several different reasons that someone’s tearfilm can become unstable, causing dry eyes. The most common is age, as tear production normally decreases as we grow older. Dry eyes can also be a symptom of other diseases that affect us as we age, such as rheumatoid arthritis.

Other causes of dry eyes may include allergies, vitamin deficiencies and overly dry climatic conditions, especially in our harsh Canadian winters. Excessive heating or air conditioning can also cause dry eyes, as can the use of drugs such as antihistamines and birth control pills.

How does it feel?

Because there are so many possible causes of dry eyes, symptoms can vary widely. One of the most common is a gritty sensation in the eye, as if there is a foreign object or particle of sand in it. Other symptoms include general eye discomfort or irritation, sensitivity to light, a tired, heavy feeling or itchiness. Red eyes are invariably associated with dry eyes, although certainly many people can have dry eyes without much redness in them at all.

An examination by an eye doctor can usually detect dry eyes. Treatment often involves the use of artificial tear solutions, many of which can be purchased over the counter at a drugstore. These solutions contain ingredients that are specially designed to restore the stability of the eye’s natural tearfilm and make the eyes feel more comfortable.

If you find over-the-counter drops are not working, contact your eye doctor, who will be able to recommend another solution that might be appropriate for you.

Don’t try to “get the red out”

One note of caution: the use of over-the-counter drops to “get the red out” is NOT recommended for the treatment of dry eyes. Many of these kinds of drops contain a substance called a vasoconstrictor, which acts to constrict blood vessels to make your eyes whiter. Your eyes may feel better temporarily, but the underlying condition is still there. In addition, when you stop using these drops, you may experience a rebound effect and your eyes may be even redder than before you began using them. This does not occur with the use of artificial tears (check the label to make sure there is no vasoconstrictor listed on the bottle).

For more information, consult your eye doctor.

The Expert:

Colour photo of Dr. Desmond Fonn

Dr. Desmond Fonnis a professor and director of the Centre for Contact Lens Research at the School of Optometry, University of Waterloo, Ontario, Canada. He is a fellow of the American Academy of Optometry, a member of the Canadian and Ontario Associations of Optometrists, and of the Association for Research in Vision and Ophthalmology.

He is the president of the International Society for Contact Lens Research and a founding member of the International Association of Contact Lens Educators in which he serves as vice president. In 2007 he was appointed associate editor-in-chief of the Eye & Contact Lens medical journal.