Dry eye syndrome
is a common cause of eye irritation.
Tears
reduce the risk of eye infection and, with each
blink of the eyelids, help clear your eyes of any
debris.
Dry eyes caused by decreased production
of fluids from your tear glands can prevent tears
from performing their useful functions and affect
your vision. An imbalance in the substances that
make up tears also can make your eyes become dry.
Common steps to
deal with dry eyes include using artificial tears
and taking steps to prevent dry eyes in the first
place
Signs and symptoms
Signs and symptoms of dry eyes may include:
-
A stinging,
burning or scratchy sensation in your eyes
-
A sense of a
foreign substance in your eyes
-
Stringy
mucus in or around your eyes
-
Increased eye
irritation from smoke or wind
-
Eye
fatigue after
short periods of reading
-
Difficulty wearing
contact lenses
Both eyes usually are affected.
Causes
Tears are much more than just water. They're a complex mixture of water,
fatty oils, proteins, electrolytes, bacteria-fighting substances and
growth factors that regulate various cell processes. This mixture helps
make the surface of your eyes smooth and clear. Without it, good vision
is impossible.
For some people, the cause of dry eyes is an imbalance in the
composition of their tears. Other people don't produce enough tears to
keep their eyes comfortably lubricated. Medications and other causes,
such as environmental factors, also can lead to dry eyes.
Poor tear quality
Your eyelids spread tears across the surface of your eyes in a
continuous thin film. The tear film has three basic layers: oil, water
and mucus. Problems with any of these layers can cause dry eye symptoms.
-
Oil.
The outer layer, produced by small glands on the edge of the eyelids
(meibomian glands), contains fatty oils called lipids. These smooth
the tear surface and slow evaporation of the middle watery layer.
When the oil layer is abnormal, the watery layer evaporates at too
fast a rate. Dry eye symptoms are common in people whose meibomian
glands are clogged. Meibomian dysfunction is more common in people
with inflammation along the edge of their eyelids (blepharitis),
rosacea and other skin disorders.
-
Water.
The middle layer, which makes up about 90 percent of tears, is
mostly water with a little bit of salt. This layer, produced by the
tear glands (lacrimal glands), cleanses your eyes and washes away
foreign particles or irritants. A shallow water layer can predispose
you to tear film instability. If your eye produces only small
amounts of water, the oil and mucus layers can touch and cause the
stringy discharge familiar to people with dry eyes.
-
Mucus.
The inner layer of mucus allows tears to spread evenly over the
surface of your eyes. Dry spots form easily in any part of the
cornea that has patchy loss of the mucus layer.
Decreased tear production
Like skin and hair, your tear production tends to dry up as you get
older. When you're unable to produce enough tears, your eyes become
easily irritated. The medical term for this condition is
keratoconjunctivitis sicca.
Although dry eyes can affect both men and women at any age, the
condition is more common among women, especially after menopause. This
may be due to hormonal changes. Damage to the tear glands from
inflammation or radiation can hamper tear production. Dry eyes are also
associated with medical conditions such as rheumatoid arthritis,
lupus,
scleroderma and Sjogren's syndrome.
Medications that may cause dry eyes
The types of common medications, both prescription and over-the-counter
(OTC), that can cause dry eyes include:
-
Diuretics, drugs
commonly used to treat high blood pressure
-
Antihistamines and
decongestants
-
Sleeping pills
-
Tricyclic
antidepressants
-
Isotretinoin-type
drugs for treatment of acne
-
Opiate-based pain
relievers such as morphine
Other causes of dry eyes
Problems unrelated to tear production or tear quality also may cause
eyes to feel dry and scratchy. These include:
-
Blepharitis, an
inflammation along the edge of the eyelids
-
Entropion, a
condition in which the eyelid turns inward
-
Ectropion, a
condition in which the eyelid sags away from the eyeball
-
Environmental
irritants such as smoke, sun, wind, low humidity, high altitudes and
indoor heating
-
Disruption of your
blink reflex
-
An allergic
reaction to eyedrops or ointments
-
Prolonged time
between blinking, such as when you're visually concentrating on
something, for example, working at a computer, driving or reading
Dry eye syndrome
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