There are two major causes of dry eye syndrome, each one connected to the quality and consistency of the tear film that lubricates the eye:

• Decreased tear production: The most common cause of dry eye syndrome is a decrease in the production of the aqueous tear layer. This is known as Aqueous tear deficiency (ATD) or lacrimal hyposecretion. The lacrimal gland is the gland responsible for tear production. As we age, the lacrimal gland lessens it’s production rate. In some cases, ATD may be a symptom of a collagen vascular disease such as rheumatoid arthritis or systemic lupus erythematosus. Certain medical drugs, including some sedatives, diuretics and oral contraceptives have been found to exacerbate and, in some cases, cause ATD. (Meadows, Michelle (May-June 2005). Dealing with Dry Eye. FDA Consumer Magazine. U.S. Food and Drug Administration).

• Excessive tear evaporation: Dry eye syndrome due to excessive tear evaporation is known medically as evaporative dry eyes. Tear production rate is not hampered. However, the rate of evaporation is abnormally accelerated. The tears lack water and, as a result, are too salty (hypertonic).

Additional causes of dry eye syndrome are eye injuries or abnormalities such as drooping eyelids or bulging eyes. The condition is also common to people who wear contact lenses. The contact lens can actually absorb the tears in the eye. Refractive surgery can also lead to dry eye syndrome during the surgery recovery period, but the condition should be alleviated over time.

Blepharitis is the medical name for inflammation of the eyelids. The condition is characterized by redness of the eyes and itchy eyelids. It is easily mistaken for dry eye syndrome. While it is different condition, blepharitis can be a contributory factor to dry eye syndrome.

As we age our bodies produce less oil. This lowering of production of oil has an impact upon the quality of the tear film. Because there is less oil to protect the watery layer, the film evaporates more quickly. This leaves dry areas on the cornea.

Environmental factors can also contribute to dry eye syndrome. Dry, windy climates contribute to excess tear evaporation as can cigarette smoke and air-conditioning.