Dry Eyes
What is the cornea?
The cornea is the clear, dome-shaped outer surface that covers the
eye in front of the iris, the colored part of the eye. The cornea helps
protect the rest of the eye from germs, dust, and other harmful matter.
The cornea bends, or refracts, light entering the eye, and accounts for
most of the eye’s total focusing power. It also serves as a filter to
screen out most of the damaging ultraviolet (UV) wavelengths in
sunlight.
The cornea is a highly organized, clear structure made up of a group of
cells and proteins precisely arranged in layers, but it has no blood
vessels to nourish or protect it against infection. Instead, it
receives its nourishment from the tears and the watery fluid (aqueous
humor) that fills the chamber behind it.
What is dry eye?
Dry eye occurs when the eye does not produce tears properly, or when
the tears are not of the correct consistency and evaporate too quickly.
In addition, inflammation of the surface of the eye may occur along
with dry eye. If left untreated, this condition can lead to pain,
ulcers, or scars on the cornea, and some loss of vision. However,
permanent loss of vision from dry eye is uncommon.
Dry eye can make it more difficult to perform some activities, such
as using a computer or reading for an extended period of time, and it
can decrease tolerance for dry environments, such as the air inside an
airplane.
What are tears, and how do they relate to dry eye?
Tears, made by the lacrimal gland, are necessary for overall eye
health and clear vision. Tears bathe the surface of the eye, keeping it
moist, and wash away dust and debris. They also help protect the eye
from bacterial and other types of infections.
Tears are composed of three major components: a) outer, oily, lipid
layer produced by the meibomian glands; b) middle, watery, lacrimal
layer produced by the lacrimal glands; and c) inner, mucous or mucin
layer produced by goblet cells located within a thin transparent layer
over the white part of the eye and covering the inner surface of the
eyelids. Tears are made of proteins (including growth factors),
electrolytes, and vitamins that are critical to maintain the health of
the eye surface and to prevent infection.
Tears are constantly produced to bathe, nourish, and protect the eye
surface. They are also produced in response to emergencies, such as a
particle of dust in the eye, an infection or irritation of the eye, or
an onset of strong emotions. When the lacrimal glands fail to produce
sufficient tears, dry eye can result.
Any disease process that alters the components of tears can make them unhealthy and result in dry eye.
What are the types of dry eye?
1) Aqueous tear-deficient dry eye is a disorder in which the
lacrimal glands fail to produce enough of the watery component of tears
to maintain a healthy eye surface.
2) Evaporative dry eye may result from inflammation of the meibomian
glands, also located in the eyelids. These glands make the lipid or
oily part of tears that slows evaporation and keeps the tears stable.
Dry eye can be associated with:
- inflammation of the surface of the eye, the lacrimal gland, or the conjunctiva;
- any disease process that alters the components of the tears;
- an increase in the surface of the eye, as in thyroid disease when the eye protrudes forward;
- cosmetic surgery, if the eyelids are opened too widely.
What are the symptoms of dry eye?
Dry eye symptoms may include any of the following:
- stinging or burning of the eye;
- a sandy or gritty feeling as if something is in the eye;
- episodes of excess tears following very dry eye periods;
- a stringy discharge from the eye;
- pain and redness of the eye;
- episodes of blurred vision;
- heavy eyelids;
- inability to cry when emotionally stressed;
- uncomfortable contact lenses;
- decreased tolerance of reading, working on the computer, or any activity that requires sustained visual attention;
- eye fatigue.
NOTE: If symptoms of dry eye persist, consult an eye care
professional to get an accurate diagnosis of the condition and begin
treatment to avoid permanent damage.
Who is likely to develop dry eye?
Elderly people frequently experience dryness of the eyes, but dry
eye can occur at any age. Nearly five million Americans 50 years of age
and older are estimated to have dry eye. Of these, more than three
million are women and more than one and a half million are men. Tens of
millions more have less severe symptoms. Dry eye is more common after
menopause. Women who experience menopause prematurely are more likely
to have eye surface damage from dry eye.
What are the causes of dry eye?
Dry eye can be a temporary or chronic condition:
- Dry eye can be a side effect of some
medications, including antihistamines, nasal decongestants,
tranquilizers, certain blood pressure medicines, Parkinson’s
medications, birth control pills and anti-depressants. - Skin disease on or around the eyelids can result in dry eye.
- Diseases of the glands in the eyelids, such as meibomian gland dysfunction, can cause dry eye.
- Dry eye can occur in women who are pregnant.
- Women who are on hormone replacement therapy may experience dry eye
symptoms. Women taking only estrogen are 70 percent more likely to
experience dry eye, whereas those taking estrogen and progesterone have
a 30 percent increased risk of developing dry eye. - Dry eye
can also develop after the refractive surgery known as LASIK. These
symptoms generally last three to six months, but may last longer in
some cases. - Dry eye can result from chemical and thermal burns that scar the membrane lining the eyelids and covering the eye.
- Allergies can be associated with dry eye.
- Infrequent blinking, associated with staring at computer or video screens, may also lead to dry eye symptoms.
- Both excessive and insufficient dosages of vitamins can contribute to dry eye.
- Homeopathic remedies may have an adverse impact on a dry eye condition.
- Loss of sensation in the cornea from long-term contact lens wear can lead to dry eye.
- Dry eye can be associated with immune system disorders such as
Sjögren’s syndrome, lupus, and rheumatoid arthritis. Sjögren’s leads to
inflammation and dryness of the mouth, eyes, and other mucous
membranes. It can also affect other organs, including the kidneys,
lungs and blood vessels. - Dry eye can be a symptom of
chronic inflammation of the conjunctiva, the membrane lining the eyelid
and covering the front part of the eye, or the lacrimal gland. Chronic
conjunctivitis can be caused by certain eye diseases, infection,
exposure to irritants such as chemical fumes and tobacco smoke, or
drafts from air conditioning or heating. - If the surface
area of the eye is increased, as in thyroid disease when the eye
protrudes forward or after cosmetic surgery if the eyelids are opened
too widely, dry eye can result. - Dry eye may occur from exposure keratitis, in which the eyelids do not close completely during sleep.
What can I do to help myself?
- Use artificial tears, gels, gel inserts, and ointments – available over
the counter – as the first line of therapy. They offer temporary relief
and provide an important replacement of naturally produced tears in
patients with aqueous tear deficiency. Avoid artificial tears with
preservatives if you need to apply them more than four times a day or
preparations with chemicals that cause blood vessels to constrict. - Wearing glasses or sunglasses that fit close to the face (wrap around
shades) or that have side shields can help slow tear evaporation from
the eye surfaces. Indoors, an air cleaner to filter dust and other
particles helps prevent dry eyes. A humidifier also may help by adding
moisture to the air. - Avoid dry conditions and allow your
eyes to rest when performing activities that require you to use your
eyes for long periods of time. Instill lubricating eye drops while
performing these tasks.
How is dry eye treated?
Depending on the causes of dry eye, your doctor may use various approaches to relieve the symptoms.
Dry eye can be managed as an ongoing condition. The first priority
is to determine if a disease is the underlying cause of the dry eye
(such as Sjögren’s syndrome or lacrimal and meibomian gland
dysfunction). If it is, then the underlying disease needs to be treated.
Cyclosporine, an anti-inflammatory medication, is the only
prescription drug available to treat dry eye. It decreases corneal
damage, increases basic tear production, and reduces symptoms of dry
eye. It may take three to six months of twice-a-day dosages for the
medication to work. In some cases of severe dry eye, short term use of
corticosteroid eye drops that decrease inflammation is required.
If dry eye results from taking a medication, your doctor may
recommend switching to a medication that does not cause the dry eye
side effect.
If contact lens wear is the problem, your eye care practitioner may
recommend another type of lens or reducing the number of hours you wear
your lenses. In the case of severe dry eye, your eye care professional
may advise you not to wear contact lenses at all.
Another option is to plug the drainage holes, small circular
openings at the inner corners of the eyelids where tears drain from the
eye into the nose. Lacrimal plugs, also called punctal plugs, can be
inserted painlessly by an eye care professional. The patient usually
does not feel them. These plugs are made of silicone or collagen, are
reversible, and are a temporary measure. In severe cases, permanent
plugs may be considered.
In some cases, a simple surgery, called punctal cautery, is
recommended to permanently close the drainage holes. The procedure
helps keep the limited volume of tears on the eye for a longer period
of time.
In some patients with dry eye, supplements or dietary sources (such
as tuna fish) of omega-3 fatty acids (especially DHA and EPA) may
decrease symptoms of irritation. The use and dosage of nutritional
supplements and vitamins should be discussed with your primary medical
doctor.
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