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Causes of Dry Eyes
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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.
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