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Some people do not produce enough tears to keep the eye
comfortable. This is known as dry eye.
Tears are produced by two different methods. One method
produces tears at a slow, steady rate and is responsible for
normal eye lubrication. The other method produces large
quantities of tears in response to eye irritation or
emotions.
Tears that lubricate are constantly produced by a healthy eye.
Excessive tears occur when the eye is irritated by a foreign body
or when a person cries.
What are the symptoms of dry eye?
- Stinging or burning eyes
- Scratchiness
- Stringy mucus in or around the eyes
- Eye irritation from smoke or wind
- Excess tearing
- Difficulty wearing contact lenses
Excess tearing from "dry eye" sounds illogical, but
if the tears responsible for maintenance lubrication do not keep
the eye wet enough, the eye becomes irritated. When the eye is
irritated, the lacrimal gland produces a large volume of tears
which overwhelms the tear drainage system. These excess tears
then overflow from your eye.
What is the tear film?
A film of tears, spread over the eye by a blink, makes the surface of the eye smooth and clear. Without our tear film, good vision would not be possible.
 The tear film consists of three layers: oily layer, watery layer and layer of mucous.
(Click on photo to enlarge)
The oily layer, produced by the meibomian glands, forms the
outermost surface of the tear film. Its main purpose is to smooth
the tear surface and reduce evaporation of tears.
The middle watery layer makes up most of what we ordinarily
think of as tears. This layer, produced by the lacrimal gland,
cleanses the eye and washes away foreign particles or
irritants.
The inner layer consists of mucus produced by the conjunctiva.
Mucus allows the watery layer to spread evenly over the surface
of the eye and helps the eye remain wet. Without mucus, tears
would not adhere to the eye.
What causes dry eye?
Tear production normally decreases as we age. Although dry eye
can occur in both men and women at any age, women are most often
affected. This is especially true after menopause.
Dry eye can also be associated with arthritis and accompanied
by a dry mouth. People with dry eyes, dry mouth and arthritis are
said to have Sjogren's syndrome.
A wide variety of common medications-prescription and
over-the- counter-can cause dry eye by reducing tear secretion.
Be sure to tell your ophthalmologist the names of all the
medications you are taking, especially if you are using:
- Diuretics
- Betablockers
- Antihistamines
- Sleeping pills
- Medications for "nerves"
- Pain relievers
Since these medications are often necessary, the dry eye
condition may have to be tolerated or treated with
"artificial tears."
People with dry eye are often more prone to the toxic side
effects of eye medications, including artificial tears. For
example, the preservatives in certain eye drops and artificial
tear prepa- rations can irritate the eye. Special
preservative-free artificial tears may be required.
How is dry eye diagnosed?
An ophthalmologist (medical eye doctor) is usually able to
diagnose dry eye by examining the eyes. Sometimes tests that
measure tear production may be necessary. One test, called the
Schirmer tear test, involves placing filter-paper strips under
the lower eye-lids to measure the rate of tear production under
various conditions. Another uses a diagnostic drop (fluorescein
or Rose Bengal) to took for certain staining patterns.
How is dry eye treated?
-- Adding tears
-- Eye drops called artificial tears are similar to your own
tears. They lubricate the eyes and help maintain moisture.
-- Artificial tears are available without a prescription.
There are many brands on the market, so you may want to try
several to find the one you like best.
-- Preservative-free eye drops are available if you are
sensitive to the preservatives in artificial tears. If you need
to use artificial tears more than every two hours,
preservative-free brands may be better for you. Solid artificial
tear inserts that are placed inside the lower lid on a daily
basis and gradually release lubricants may be beneficial to some
people.
You can use the tears as often as necessary--once or twice a
day or as often as several times an hour.
Conserving the tears
Conserving your eyes' own tears is another approach to
keeping the eyes moist. Tears drain out of the eye through a
small channel into the nose (that is why your nose runs when you
cry). Your ophthalmologist may close these channels either
temporarily or permanently. The closure conserves your own tears
and makes artificial tears last longer.
Other methods
Tears evaporate like any other liquid. You can take steps to
prevent evaporation. In winter, when indoor heat is on, a
humidifier or a pan of water on the radiator adds moisture to dry
air. Wrap- around glasses may reduce the drying effect of the
wind, but are illegal to wear while driving in some states.
Anything that may cause dryness, such as an overly warm room,
hair dryers or wind, should be avoided by a person with dry eye.
Smoking is especially bothersome.
Some people with dry eye complain of scratchy eyes" when
they wake up. This symptom can be treated by using an artificial
tear ointment at bedtime. Use the smallest amount of ointment
necessary for comfort, since the ointment can cause your vision
to blur temporarily.
Dry eye due to a lack of vitamin A in the diet is rare in the
United States but is more common in poorer countries, especially
among children. Ointments containing vitamin A can help dry eye
if it is caused by unusual conditions such as Stevens-Johnson
syndrome or pemphigoid. Vitamin A supplements do not seem to help
people with ordinary dry eye.
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