Dry Eye Syndrome
What Is Dry Eye Syndrome (DES)?
Dry eye syndrome (DES) is a common eye problem, affecting a significant percentage of the population. Dry eye syndrome is seen in people of any race, age or sex, although it's more common in older patients and more common in women than in men.
What Are the Types of Dry Eye Syndrome?
Types of dry eye syndrome are related to the underlying problem that leads to dry eyes:
- Insufficient production of tears (also called keratoconjunctivitis sicca)
- Poor retention of tears
- Excessive evaporation of tears
What Are Causes of Dry Eye Syndrome?
Dry eye syndrome results from problems stemming from any of three layers of the tear film (a normal, thin layer of tears that covers the eye):
- The innermost layer is the mucin (or mucus) layer. It is produced by the conjunctiva (the clear membrane that lines the eye). The mucus helps the overlying watery layer to spread evenly over the eye.
- The middle layer is the watery (or aqueous) layer. It is essentially a very dilute salty solution. The lacrimal glands located under the upper lids produce this watery layer. This layer's function is to keep the eye moist and comfortable, as well as to help flush out any dust, debris, or foreign objects that may get into the eye. It's this tear layer that flows when we're crying or when the eyes are irritated.
- The outermost layer is the oily layer. These oils are produced by the meibomian glands, which are located on the eyelids. This important layer helps block evaporation of the watery layer between blinks.
The innermost mucin layer can be abnormal if there has been injury to the conjunctiva, for example after a chemical burn, Stevens-Johnson syndrome, cicatricial pemphigoid, malnutrition, or other inflammatory or autoimmune disorders.
The middle watery layer can be insufficient if the lacrimal glands are not functioning properly. This is seen in a variety of settings, including Sjögren's syndrome, rheumatoid arthritis, or lupus and other autoimmune disorders. Some medications, including antihistamines, antidepressants, and beta-blockers, may also decrease tear production.
The outermost oily layer may be poor if the eyelids' meibomian glands are plugged or clogged. This is often seen in meibomian gland dysfunction, blepharitis, and acne rosacea.
The eyelids can also play a role in causing dry eye syndrome if blinking is decreased or if the eyelids cannot close all the way.
- When you read, watch TV, or perform a task that requires close attention with your eyes, you may not blink as frequently. This decreased blinking allows excessive evaporation of the tears.
- Certain health conditions, such as stroke, Bell's palsy, or thyroid eye disease, can make it difficult to close your eyes on your own.
- Abnormal eyelid position following surgery, trauma, or certain skin conditions can also interfere with producing and maintaining a healthy tear film.
- Eyes can also be dry when exposed to wind from fans and vents.
Medically Reviewed by a Doctor on 7/26/2017
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