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Dry Eye Syndrome

The healthy eye constantly produces tears that lubricate. When a foreign body irritates the eye or when a person cries, more tears are produced. Tears must have the right balance of oil, water, and mucus to be able to protect your eyes. Without this balance, your eyes become dry and irritated and produce too many tears.  Dry eye syndrome (DES) is a common disorder of the tear film, affecting a significant percentage of the population, especially those older than 40 years.

Tears are comprised of three layers.  The mucus layer coats the cornea, the eye’s clear outer window, forming a foundation so the tear film can adhere to the eye.  The middle aqueous layer provides moisture and supplies oxygen and other important nutrients to the cornea.  This layer is made of 98 percent water along with small amounts of salt, proteins and other compounds.  The outer lipid layer is an oily film that seals the tear film on the eye and helps to prevent evaporation.

Tears are formed in several glands around the eye.  The water layer is produced in the lacrimal gland, located under the upper eyelid.  Several smaller glands in the lids make the oil and mucus layers.  With each blink, the eyelids spread the tears over the eye.  Excess tears flow into two tiny drainage ducts in the corner of the eye by the nose.  These ducts lead to tiny canals that connect to the nasal passage.  The connection between the tear ducts and the nasal passage is the reason that crying causes a runny nose.

Causes
•Decreased tear production
•Excessive tear evaporation
•An abnormality in the production of mucus or lipids normally found in the tear layer
Aqueous (watery) tear deficiency is caused by either poor production of watery tears or excessive evaporation of the watery tear layer.
•Poor production of tears by the tear glands may be a result of age, hormonal changes, or various autoimmune diseases, such as primary Sj?gren syndrome, rheumatoid arthritis, or lupus.
•Evaporative loss of the watery tear layer is usually a result of an insufficient overlying lipid layer.
•Some medications, such as antihistamines, antidepressants, beta-blockers, and oral contraceptives, may decrease tear production.
If blinking is decreased or if the eyelids cannot be closed, the eyes may dry out because of tear evaporation.
•When you read, watch TV, or perform a task that requires close attention with your eyes, you do not blink as often. This decreased blinking allows excessive evaporation of the tears.
•Certain conditions, such as stroke or Bell palsy, make it difficult to close your eyes on your own. As a result, your eyes may become dry from tear evaporation.
•Abnormal production of mucin by the conjunctiva may occur.
•This can result from chemical (alkali) burns to the eye or because of different autoimmune diseases, such as Stevens-Johnson syndrome and cicatricial pemphigoid.
•This abnormal production leads to poor spreading of the tears over the surface of the eye. The surface of the eye can dry out and even become damaged, even though more than enough watery tears may be present.

 
Symptoms
Discomfort in the eyes ranging from a light pain to a grainy, scratchy feeling in the eyes is possible. The eyes may also become itchy, red, or tears may start to flood the eyes. People with dry eyes will generally experience strain when using the eyes on focusing tasks like watching the TV, knitting, and other activities.
•Stinging or burning
•Eye irritation or scratchiness
•Excess tearing, especially when reading, driving, or watching television
•Stringy mucus in or around the eyes
•Difficulty wearing contact lenses

Diagnosis
Testing for dry eyes can be performed through Schirmer's test, is performed by placing a small piece of filter paper inside the lower part of the eyelids. The eyes are closed for a few minutes and taken out to measure the amount of tear production. The Schirmer's test can determine if there is difficulty in tear production or if the tears are not efficient in maintaining eye health.

Treatment
Replacing natural tears with artificial tears is the basis of treatment. Artificial tears are available and are used as eye drops to lubricate the eyes and replace the missing moisture.
Some patients with mild dryness may benefit from blinking more frequently, especially when reading, driving, or watching television.
Conserving the naturally produced tears is another approach to keeping the eyes moist. After bathing the eye's surface, tears enter a small opening in each lid, the punctum, and drain through a small canal, the canaliculus, into the lacrimal sac and down the naso-lacrimal duct into the nose. These channels may be closed temporarily, or permanently, by your ophthalmologist. The closure creates a reservoir of tears which allows the eyes to stay moist for longer periods of time.

Dry Eye Prevention Tips
•Drink plenty of water to keep the body moisturized.
•Both furnaces in the winter and air conditioning in the summer decrease the humidity in the air. Minimize there use.
•Avoid having excessive air movement by decreasing the speed of ceiling fans and/or oscillating fans.
•If you notice your eyes are dry mainly while you are reading or watching TV, taking frequent breaks to allow your eyes to rest and become moist and comfortable again is helpful.
•Get plenty of sleep to keep eyes healthy.

Consequences of Dry Eye
Dry eye is caused by an increased rate of evaporation of the tear film or a decreased rate of production of the tear film. Over time, dry eye can lead to vision problems, causing sufferers to need stronger lens prescriptions every two years. In addition, dry eye can contribute to eye redness and tearing as well as wrinkles.

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