Dry Eye Syndrome (cont.)
What Causes Dry Eyes?
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.
Medically Reviewed by a Doctor on 8/31/2015
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