Dry eye syndrome is caused by a chronic lack of sufficient lubrication and moisture on the surface of the eye.  It causes minimal irritation to inflammation of the anterior (front) tissues of the eye.

Dry eyes also are described by the medical term, keratitis sicca, which generally means decreased quality or quantity of tears.

Dry Eye Symptoms

Persistent dryness, scratchiness and a burning sensation are common symptoms of dry eyes. These symptoms alone may prompt your Dr. of Optometry to diagnose dry eye syndrome.  Sometimes your eye doctor may want to measure the amount of tears in your eyes. A thin strip of filter paper placed under the lower eyelid, called a Schirmer test, is one way to measure tear production.

Another symptom of dry eyes is a "foreign body sensation," which is a scratchy feeling like something is in your eye.

And it may seem odd, but dry eye syndrome also can cause watery eyes. This is because dryness on the eye's surface sometimes will overstimulate production of the watery component of your tears as a protective mechanism.

What Causes Dry Eyes

Tears bathe the eye, flushing out dust and debris and keeping the eye moist. They also contain enzymes that neutralize microorganisms that colonize the eye. Tears are essential for good eye health.  They are complex, containing many different essential elements, including oils produced by special glands in the eyelids called meibomian glands. These oils prevent natural evaporation of the tears.

In dry eye syndrome, the lacrimal gland or associated glands near the eye do not produce enough tears, or dysfunction of the meibomian glands reduces oil output, leading to excessive evaporation of the tears. This is called evaporative dry eye and is now considered to be the primary cause of most cases of dry eye.

Dry eye syndrome has many causes. It occurs as a part of the natural aging process (especially during menopause in women); as a side effect of many medications, such as antihistamines, antidepressants, certain blood pressure medicines, Parkinson's medications and birth control pills; or because you live in a dry, dusty or windy climate.

If your home or office has air conditioning or a dry heating system, that also can dry out your eyes. Another cause is inadequate blinking, such as when you're staring at a computer screen all day.

Dry eyes also are a symptom of some systemic diseases such as lupus, rheumatoid arthritis, ocular rosacea or Sjogren’s disease which is a combination of dry eyes, dry mouth and rheumatoid arthritis or lupus.