Dry Eye (Ocular Surface Disease) syndrome is caused by a chronic lack of sufficient lubrication and moisture on the surface of the eye.
Its consequences range from subtle but constant irritation to inflammation of the anterior (front) tissues of the eye. Another symptom of dry eyes is a "foreign body sensation," which is a feeling that something is in your eye.
Although it may seem odd, dry eye syndrome can also cause watery eyes. This is because dryness on the eye's surface sometimes will over stimulate production of the watery component of your tears as a protective mechanism.