What is Glaucoma?
Glaucoma is an eye disease which is one of the leading causes of blindness in the United
States. Glaucoma is fairly common in adults over age 35. Two out of every 100 persons
in this age group have vision threatened by this disease. When diagnosed early, blindness
from glaucoma is almost always preventable. When we look at an object, the image is carried
from the retina to the brain by the nerve of sight (the optic nerve). This nerve is like
an electric cable. it contains a million wires, each carrying a message to the brain,
which join together to provide side vision, as well as sharp, central reading vision.
Glaucoma can produce damage to these "wires," causing blind spots in areas of vision to
develop. People seldom notice these blind areas in the side vision until considerable
optic nerve damage has occured. If the entire nerve is destroyed, blindness results.
Fortunately, this rarely occurs if glaucoma is diagnosed and treated before major damage
has taken place. The key to preventing optic nerve damage or blindness from glaucoma is
early diagnosis and treatment. Eye doctors (Optometrist, Optometric Physician or Ophthalmologist)
test for glaucoma as part of a comprehensive eye examination. Medical eye examinations are the best
defense against glaucoma. For this reason, adults should see an eye doctor for periodic eye
Cause and symptoms.
A clear transparent liquid called the aqueous humor flows through the inner eye continuously. This
inner flow can be compared to a sink with the faucet turned on all the time. If the drainpipe
gets clogged, water collects in the sink. If the drainage system of the eye gets similarly
blocked, the fluid pressure within the inner eye is increased and can cause damage to the optic
Blockage of these "pipes" can occur in 4 ways:
- Most commonly, the "drainpipe" can become smaller with age, clogged by deposits
which build up slowly. This partial blockage causes a gradual increase of pressure within the
eye. This is known as chronic open-angle glaucoma because it develops slowly over a period of
time. Most adult glaucoma patients have this type of glaucoma. Chronic open-angle glaucoma
can steal vision so quietly that the patient is unaware of trouble until the optic nerve is badly
damaged. Because no symptoms occur, the best way to diagnose this form of glaucoma is by
periodic medical eye examination.
- Second, the "drainpipe" may have been poorly manufactured. This type of defect
is seen in congenital glaucoma, where the drainage openings are abnormal from birth. Since an infant's
eye has more elasticity than an adult's, when pressure inside the eye is increased, the easily
stretchable eye may enlarge. The front of the eye may become cloudy like fog on a windshield.
The infant may be sensitive to light and tear excessively. This is a rare condition. However,
such symptoms or other suspicion of trouble in the eyes of an infant or child should lead to
an immediate visit to an eye doctor.
- Third, a sheet of paper may float near the drain, suddenly drop over the opening,
close up the drainage area, and block all the outflow. In the eye, the iris may act like the
sheet of paper and press up against the drainage area and close it off. Fluid backs up and
increases eye pressure rapidly. Such a sudden, complete blockage of fluid flowing out of the
eye results in acute angle-closure glaucoma. Blurred vision, severe pain, rainbow haloes
around lights, nausea and vomiting should bring the patient quickly to an eye doctor. Unless
this condition is relieved promptly, blindness can result in a day or two.
- Fourth, other conditions including injuries, certain drugs, hemorrhages, tumors,
and inflammations can sometimes block outflow channels in the eye. This may increase inner
eye pressure and lead to secondary glaucoma.
Detection and diagnosis.
Early diagnosis can be made by your eye doctor in the course of a periodic eye examination. During
the painless examination, the eye doctor will determine the pressure of the eye. This is only part
of the examination for glaucoma. Using an instrument called an ophthalmoscope, the doctor will
examine the back of your eye to see if the optic nerve is healthy and that no damage is occurring.
Sometimes, side vision will be tested for shrinkage or blind spots. If necessary, still other tests
may be done. On occasion, a patient will be found to have an eye pressure over the normal range,
but no evidence of damage from glaucoma. Some people seem to tolerate high eye pressures
without ever developing loss of vision. However, in these cases it is important for the eye doctor
to consider additional causes which may add to a person's risk of developing damage from glaucoma.
A history of glaucoma in the family, or general health problems such as diabetes, hardening of the
arteries, or anemia are examples of risk factors. Black patients are also at an increased risk for
glaucoma. The eye doctor must weigh all these factors before deciding whether a patient needs
treatment for glaucoma, or whether the patient should be monitored closely as a glaucoma suspect
since the risk of developing glaucoma is higher than normal.
Glaucoma is usually controlled with eye drops given 2 to 4 times a day or by pills given in
various combinations. These medications act to decrease eye pressure either by assisting flow
of fluid out of the eye or by decreasing the amount of fluid entering the eye. To be effective,
these medications must be taken regularly and continuously. Patients with any type of glaucoma
need periodic examination. Glaucoma sometimes gets worse (or better) without the patient being
aware of it, and as a result, treatment may need to be changed after awhile. As a rule, damage
caused by glaucoma cannot be reversed. Eye drops, pills, and surgery are used to prevent
further damage from occurring, and to preserve existing vision. However, treatment may
occasionally result in unwanted side effects. Some eye drops may sting, redden the eye and
cause blurring or occasional headaches. Such side effects usually disappear after a few
weeks. Though rare, other drops may affect the pulse, heartbeat, and breathing. Pills
sometimes cause tingling of fingers and toes, drowsiness, loss of appetite, bowel irregularities,
and occasional kidney stone formation. They are usually prescribed only when absolutely
necessary. You should notify your eye doctor immediately if there is a question of possible
Glaucoma and you.
Control of glaucoma by drugs can only be effective if patients adhere to the treatment schedule prescribed
by their eye doctor. The treatment "team" is made up of both you and your doctor. Medication
should never be stopped without first consulting your eye doctor. It is always important to
inform all the physicians you visit about the eye medications you are using. Remember, it is your
vision, and you must do your part in maintaining it. If medications are poorly tolerated or not
effective in controlling glaucoma, surgery may become necessary. In some cases, almost painless
surgery without an incision can be done with the laser beam. In other cases, a cut in the eye to form
a new drainage canal is necessary. Complications such as cataract or infection may occur.
Fortunately, serious complications of modern glaucoma surgery are rare. In most cases, recommended
surgery is safer than permitting continuing loss of the optic nerve from glaucoma.
Loss of vision is largely preventable.
If you are over age 35, you should have your eyes checked for glaucoma every 2 or 3 years. Your eye
doctor should be consulted whenever there is any decrease in vision or recurrent pain, or when any
of the other symptoms discussed here are present. When diagnosed promptly, eye pressure can be
brought under control and future glaucoma attacks can be prevented.