Dry Eye Syndrome (cont.)
What Are Causes of Dry Eye Syndrome?
Dry eye syndrome is a common disorder of the normal tear film that results from one of the following:
- 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 health conditions like autoimmune diseases such as primary Sjogren 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 may not blink as often. This decreased blinking allows excessive evaporation of the tears.
- Certain health conditions, such as stroke or Bell's 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 as a result of different health conditions, such as Stevens-Johnson syndrome and cicatricial pemphigoid.
- This abnormal production of mucin 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.
Insufficient lipid layers are the result of meibomian gland dysfunction, as with rosacea or as a result of taking oral isotretinoin medication.
- Meibomian glands are the oil glands in the eyelids that produce the lipid layer.
- If the oil glands become blocked or if the oil is too thick, there may not be enough oil to cover the watery tear layer to prevent its evaporation.
- Also, if an infection is present along the eyelids or the eyelashes, called blepharitis, the bacteria may breakdown the oil so there may not be enough oil.
What Are Signs and Symptoms of Dry Eye Syndrome?
If you have DES, you may also experience the following symptoms:
- Dry, gritty/scratchy, or filmy feeling in the eyes
- Burning or itching in the eyes
- Redness of the eyes
- Blurred vision
- A sensation of having a foreign body in the eyes
- Light sensitivity
Symptoms seem to worsen in dry climates, in windy conditions, with higher temperatures, with lower humidity, with prolonged use of your eyes (for example, reading, watching TV), and toward the end of the day.
Sometimes a symptom of DES may actually be intermittent excessive tearing with DES. When your eye becomes slightly dry and irritated, it may initiate reflex tearing with production of a large amount of tears all at once to try to get moist and comfortable again. Unfortunately, your eye can only handle so many tears at any one time; the rest pour over your eyelids and down your cheeks. Those tears that pour down your cheeks do not help your eyes and are wasted. A short time later, your eyes will become slightly dry and irritated again, and the whole process may repeat itself.
Medically Reviewed by a Doctor on 8/31/2015
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