Glaucoma is a group of diseases that can
lead to damage to the eye's optic nerve and result in blindness
"
With early treatment, you can often protect
your eyes against serious vision problems.
"
Glaucoma is a group of diseases that
can lead to damage to the eye's optic nerve and result in blindness.
Open-angle glaucoma, the most common form of glaucoma,
affects about 3 million Americans--half of whom don't know they
have it. It has no symptoms at first. But over the years it can
steal your sight. With early treatment, you can often protect
your eyes against serious vision problems.
----------------------------
What is the optic nerve?
The optic nerve is a bundle of more than 1 million nerve fibers.
It connects the retina, the light-sensitive layer of tissue at
the back of the eye, with the brain (see diagram). A healthy optic
nerve is necessary for good vision.
----------------------------
How does glaucoma damage the optic nerve?
In many people, increased pressure inside the eye causes glaucoma.
In the front of the eye is a space called the anterior chamber.
A clear fluid flows continuously in and out of this space and
nourishes nearby tissues.
The fluid leaves the anterior chamber at the angle where the
cornea and iris meet (see diagram). When the fluid reaches the
angle, it flows through a spongy meshwork, like a drain, and leaves
the eye.
Open-angle glaucoma gets its name because the angle that
allows fluid to drain out of the anterior chamber is open. However,
for unknown reasons, the fluid passes too slowly through the meshwork
drain. As the fluid builds up, the pressure inside the eye rises.
Unless the pressure at the front of the eye is controlled, it
can damage the optic nerve and cause vision loss.
----------------------------
Who is at risk?
Although anyone can get glaucoma, some people are at higher
risk than others. They include:
- Blacks over age 40.
- Everyone over age 60.
- People with a family history of glaucoma.
----------------------------
What are the symptoms of glaucoma?
At first, open-angle glaucoma has no symptoms. Vision stays
normal, and there is no pain. As glaucoma remains untreated, people
may notice that although they see things clearly in front of them,
they miss objects to the side and out of the corner of their eye.
Without treatment, people with glaucoma may find that
they suddenly have no side vision. It may seem as though they
are looking through a tunnel. Over time, the remaining forward
vision may decrease until there is no vision left.
----------------------------
How is glaucoma detected?
Most people think that they have glaucoma if the pressure in
their eye is increased. This is not always true. High pressure
puts you at risk for glaucoma. It may not mean that you have the
disease.
Whether or not you get glaucoma depends on the level of pressure
that your optic nerve can tolerate without being damaged. This
level is different for each person.
Although normal pressure is usually between 12-21 mm
Hg, a person might have glaucoma even if the pressure is in this
range. That is why an eye examination is very important.
----------------------------
To detect glaucoma, your eye care professional will do the
following tests:
Visual acuity: This eye chart test measures how well
you see at various distances.
Visual Field: This test measures your side (peripheral)
vision. It helps your eye care professional find out if you have
lost side vision, a sign of glaucoma.
Pupil dilation: This examination provides your eye care
professional with a better view of the optic nerve to check for
signs of damage. To do this, your eye care professional places
drops into the eye to dilate (widen) the pupil. After the examination,
your close-up vision may remain blurred for several hours.
Tonometry: This standard test determines the fluid pressure
inside the eye. There are many types of tonometry. One type uses
a purple light to measure pressure. Another type is the "air puff,"
test, which measures the resistance of the eye to a puff of air.
----------------------------
Can glaucoma be treated?
Yes. Although you will never be cured of glaucoma, treatment
often can control it. This makes early diagnosis and treatment
important to protect your sight. Most doctors use medications
for newly diagnosed glaucoma; however, new research findings show
that laser surgery is a safe and effective alternative.
----------------------------
Glaucoma treatments include:
Medicine: Medicines are the most common early treatment
for glaucoma. They come in the form of eyedrops and pills. Some
cause the eye to make less fluid. Others lower pressure by helping
fluid drain from the eye.
Glaucoma drugs may be taken several times a day. Most
people have no problems. However, some medicines can cause headaches
or have side effects which affect other parts of the body. Drops
may cause stinging, burning, and redness in the eye. Ask your
eye care professional to show you how to put the drops into your
eye. In addition, tell your eye care professional about other
medications you may be taking before you begin glaucoma treatment.
Many drugs are available to treat glaucoma. If you have problems
with one medication, tell your eye care professional. Treatment
using a different dosage or a new drug may be possible.
You will need to use the drops and/or pills as long as
they help to control your eye pressure. This is very important.
Because glaucoma often has no symptoms, people may be tempted
to stop or may forget to take their medicine.
Laser surgery (also called laser trabeculoplasty): Laser
surgery helps fluid drain out of the eye. Although your eye care
professional may suggest laser surgery at any time, it is often
done after trying treatment with medicines. In many cases, you
will need to keep taking glaucoma drugs even after laser surgery.
Laser surgery is performed in an eye care professional's office
or eye clinic. Before the surgery, your eye care professional
will apply drops to numb the eye.
As you sit facing the laser machine, your eye care professional
will hold a special lens to your eye. A high-energy beam of light
is aimed at the lens and reflected onto the meshwork inside your
eye. You may see flashes of bright green or red light. The laser
makes 50-100 evenly spaced burns. These burns stretch the drainage
holes in the meshwork. This helps to open the holes and lets fluid
drain better through them.
Your eye care professional will check your eye pressure
shortly afterward. He or she may also give you some drops to take
home for any soreness or swelling inside the eye. You will need
to make several followup visits to have your pressure monitored.
Once you have had laser surgery over the entire meshwork, further
laser treatment may not help. Studies show that laser surgery
is very good at getting the pressure down. But its effects sometimes
wear off over time. Two years after laser surgery, the pressure
increases again in more than half of all patients.
Conventional surgery: The purpose of surgery is to make
a new opening for the fluid to leave the eye. Although your eye
care professional may suggest it at any time, this surgery is
often done after medicine and laser surgery have failed to control
your pressure.
Surgery is performed in a clinic or hospital. Before the surgery,
your eye care professional gives you medicine to help you relax
and then small injections around the eye to make it numb.
The eye care professional removes a small piece of tissue
from the white (sclera) of the eye. This creates a new channel
for fluid to drain from the eye. But surgery does not leave an
open hole in the eye. The white of the eye is covered by a thin,
clear tissue called the conjunctiva. The fluid flows through the
new opening, under the conjunctiva, and drains from the eye.
You must put drops in the eye for several weeks after the operation
to fight infection and swelling. (The drops will be different
than the eyedrops you were using before surgery.) You will also
need to make frequent visits to your eye care professional. This
is very important, especially in the first few weeks after surgery.
In some patients, surgery is about 80 to 90 percent effective
at lowering pressure. However, if the new drainage opening closes,
a second operation may be needed. Conventional surgery works best
if you have not had previous eye surgery, such as a cataract operation.
Keep in mind that while glaucoma surgery may save remaining
vision, it does not improve sight. In fact, your vision may not
be as good as it was before surgery.
Like any operation, glaucoma surgery can cause side effects.
These include cataract, problems with the cornea, inflammation
or infection inside the eye, and swelling of blood vessels behind
the eye. However, if you do have any of these problems, effective
treatments are available.
----------------------------
What are some other forms of glaucoma?
Although open-angle glaucoma is the most common form, some people
have other forms of the disease.
In low-tension or normal-tension glaucoma, optic nerve damage
and narrowed side vision occur unexpectedly in people with normal
eye pressure. People with this form of the disease have the same
types of treatment as open-angle glaucoma.
In closed-angle glaucoma, the fluid at the front of the
eye cannot reach the angle and leave the eye because the angle
gets blocked by part of the iris. People with this type of glaucoma
have a sudden increase in pressure. Symptoms include severe pain
and nausea as well as redness of the eye and blurred vision. This
is a medical emergency. The patient needs immediate treatment
to improve the flow of fluid. Without treatment, the eye can become
blind in as little as one or two days. Usually, prompt laser surgery
can clear the blockage and protect sight.
In congenital glaucoma, children are born with defects
in the angle of the eye that slow the normal drainage of fluid.
Children with this problem usually have obvious symptoms such
as cloudy eyes, sensitivity to light, and excessive tearing. Surgery
is usually the suggested treatment, because medicines may have
unknown effects in infants and be difficult to give to them. The
surgery is safe and effective. If surgery is done promptly, these
children usually have an excellent chance of having good vision.
Secondary glaucomas can develop as a complication of
other medical conditions. They are sometimes associated with eye
surgery or advanced cataracts, eye injuries, certain eye tumors,
or uveitis (eye inflammation). One type, known as pigmentary glaucoma,
occurs when pigment from the iris flakes off and blocks the meshwork,
slowing fluid drainage.
A severe form, called neovascular glaucoma, is linked
to diabetes. Also, corticosteroid drugs—used to treat eye inflammations
and other diseases--can trigger glaucoma in a few people. Treatment
is with medicines, laser surgery, or conventional surgery.
----------------------------
What research is being done?
The National Eye Institute (NEI) is the Federal government's
lead agency for vision research. The NEI is supporting many research
studies both in the laboratory and with patients. This research
should provide better ways in the future to detect, treat, and
prevent vision loss in people with glaucoma.
For instance, researchers recently found a gene that
causes a form of glaucoma that starts at a young age. This is
the first glaucoma gene ever located. This finding could help
us learn more about how glaucoma damages the eye.
The NEI is also supporting clinical studies that will tell us
more about who is likely to get glaucoma, when to treat people
with increased pressure, and which treatment to use first.
----------------------------
What can you do to protect your vision?
If you are being treated for glaucoma, be sure to take your
glaucoma medicine every day and see your eye care professional
regularly.
You can also help protect the vision of family members and friends
who may be at high risk for glaucoma--Blacks over age 40 and everyone
over age 60. Encourage them to have an eye examination through
dilated pupils every two years.
----------------------------
For more information about glaucoma, you may wish to contact:
American Academy of Ophthalmology
655 Beach Street
San Francisco, CA 94109-7424
(415) 561-8500
http://www.eyenet.org
American Optometric Association
243 Lindbergh Boulevard
St. Louis, MO 63141
(314) 991-4100
Email: AmOptCCC@aol.com
http://www.aoanet.org
(The) Glaucoma Foundation
33 Maiden Lane
New York, NY 10038
1-800-452-8266
(212) 285-0080
Email: glaucomafdn@mindspring.com
http://www.glaucoma-foundation.org/info
Glaucoma Research Foundation
200 Pine Street, Suite 200
San Francisco, CA 94104
1-800-826-6693
(415) 986-3162
http://www.glaucoma.org
National Eye Institute
2020 Vision Place
Bethesda, MD 20892-3655
(301) 496-5248
Email: 2020@nei.nih.gov
http://www.nei.nih.gov
Prevent Blindness America
500 East Remington Road
Schaumburg, IL 60173
1 (800) 331 -2020
(847) 843-2020
http://prevent-blindness.org
National Eye Institute
National Institutes of Health
NIH Publication No. 99-651
April 2000
Related Links:
|
