Keratoconjunctivitis sicca (KCS), also called keratitis sicca, xerophthalmia or dry eye syndrome (DES)  is an eye disease caused by eye dryness, which, in turn, is caused by either decreased tear production or increased tear film evaporation. It is found in humans and some animals. The phrase "keratoconjunctivitis sicca" is Latin, and its literal translation is "dry inflammation of the cornea and conjunctiva".
Typical symptoms of keratoconjunctivitis sicca are dryness, burning and a sandy-gritty eye irritation that gets worse as the day goes on. Symptoms may also be described as itchy,scratchy, stingy or tired eyes. Other symptoms are pain,redness,
a pulling sensation, and pressure behind the eye.There may be a feeling that something, such as a speck of dirt in the eye. The resultant damage to the eye surface increases discomfort and sensitivity to bright light. Both eyes usually are affected.
Abnormal tear composition:
Keratoconjunctivitis sicca can also be caused by abnormal tear composition resulting in rapid evaporation or premature destruction of the tears. When caused by rapid evaporation, it is termed evaporative dry eyes. In this, although the tear gland produces a sufficient amount of tears, the rate of evaporation of the tears is too rapid. There is a loss of water from the tears that results in tears that are too "salty" or hypertonic. As a result, the entire conjunctiva and cornea cannot be kept covered with a complete layer of tears during certain activities or in certain environments.
Dry eyes can usually be diagnosed by the symptoms alone. Tests can determine both the quantity and the quality of the tears. A slit lamp examination can be performed to diagnose dry eyes and to document any damage to the eye.
A Schirmer's test can measure the amount of moisture bathing the eye.This test is useful for determining the severity of the condition. A five-minute Schirmer's test with and without anesthesia using a Whatman #41 filter paper 5 mm wide by 35 mm long is performed. For this test, wetting under 5 mm with or without anesthesia is considered diagnostic for dry eyes.
A variety of approaches can be taken to treatment. These can be summarized as: avoidance of exacerbating factors, tear stimulation and supplementation, increasing tear retention, eyelid cleansing and treatment of eye inflammation.