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Glaucoma is a leading cause of blindness in the United States,
especially for older people. But loss of sight from glaucoma is
often preventable if you get treatment early enough.
 Glaucoma
is a disease of the optic nerve. The optic nerve carries the images
we see to the brain. Many people know that glaucoma has something
to do with pressure inside the eye. High pressure inside the eye
is a risk factor for developing glaucoma, although many people with
"normal range" pressures develop the disease.
The optic nerve is made up of a huge number of nerve fibers, like
an electric cable containing a hugh number of wires. Glaucoma can
damage nerve fibers, causing blind spots to develop.
Usually people don't notice these blind areas until much optic
nerve damage has already occurred. If the entire nerve is destroyed,
blindness results.
Early detection and treatment by your ophthalmologist are the keys
to preventing optic nerve damage and blindness from glaucoma.
What Causes Glaucoma?
Clear liquid, called the aqueous humor, circulates inside the eye.
A small amount of this fluid is produced constantly, and an equal
amount flows out of the eye through a mircoscopic drainage system.
(This liquid is not part of the tears on the outer surface of the
eye.) You can think of the flow of aqueous fluid as a sink with
the faucet turned on all the time.
(Under picture) The clear liquid aqueous humor is constantly being
produced within the eye (left). If the drainage angle of the eye
is blocked, excess fluid cannot flow out of the eye (right).
If the "drainpipe" gets clogged, water collects in the
sink and the sink may overflow. Because the eye is a closed structure,
the excess fluid cannot overflow if the drain is clogged. If the
drainage area of the eye—called the drainage angle—is
blocked, the fluid pressure within the inner eye may increase, which
can damage the optic nerve.
What are the different types of glaucoma?
Chronic open-angle glaucoma: This is the most common form of
glaucoma in the United States. It occurs as a result of the drainage
angle of the eye becoming less efficient with time, and pressure
within the eye gradually increasing.
If this increased pressure results in optic nerve damage, it is
known as chronic open-angle glaucoma. Over 90% of adult glaucoma
patients have this type of glaucoma.
Chronic open-angle glaucoma damages vision so gradually and painlessly
that you are not aware of trouble until the optic nerve is already
badly damaged.
Angle-closure glaucoma: Sometimes the drainage angle of the eye
may become physically blocked by a narrow angle. In the eye, the
iris (the part that makes eyes blue or brown) and the cornea form
the chamber angle, which houses the drainage tissue.
If the angle is narrow, it can close off the drainage tissue slowly
over time, or suddenly.
Symptoms may include:
- Blurred vision
- Severe eye pain
- Headache
- Rainbow haloes around lights
- Nausea and vomiting
- If you have any of these symptoms, call your ophthalmologist
immediately. Unless an ophthalmologist treats acute angle-closure
glaucoma quickly, blindness can result.
- Acute angle-closure glaucoma is more common in Asian people
than in people of European descent; it is rare in people of African
descent.
In some patients glaucoma has features of both the open-angle type
and the angle-closure type, called mixed mechanism glaucoma. It
occurs more frequently in people of African and Asian descent.
How is glaucoma detected?
Regular eye examinations by your ophthalmologist are the best way
to detect glaucoma. An ophthalmologist is a medical doctor. Your
ophthalmologist can detect and treat glaucoma.
During a complete and painless examination, your ophthalmologist
will:
- Measure your intra ocular pressure (tonometry);
- Inspect the drainage angle of your eye (gonioscopy);
- Evaluate any optic nerve damage (ophthalmoscopy);
- Test the visual field of each eye (perimetry).
Who is at risk for glaucoma?
High pressure alone does not mean that you have glaucoma, and you
can develop glaucoma even with normal pressures. Your ophthalmologist
puts together many kinds of information to determine your risk for
developing the disease.
The most important risk factors include:
- Age
- African ancestry
- A family history of glaucoma
- Past injuries to the eyes
- Your ophthalmologist will weigh all of these factors before
deciding whether you need treatment for glaucoma, or whether you
should be monitored closely as a glaucoma suspect.
This means your risk of developing glaucoma is higher than normal,
and you need to have regular examinations to detect the early signs
of damage to the optic nerve.
How is glaucoma treated?
As a rule, damage caused by glaucoma cannot be reversed. Eye
drops, pills, and laser and surgical operations are used to prevent
or slow further damage from occurring.
With any type of glaucoma, periodic examinations are very important
to prevent vision loss. Because glaucoma can worsen without your
being aware of it, your treatment may need to be changed over time.
Medicines
Glaucoma may be controlled with eye drops, sometimes in combination
with pills. These medications decrease eye pressure, either by slowing
the production of aqueous fluids within the eye or by improving
the flow through the drainage angle.
For these medications to work, you must take them regularly and
continuously. It is also important to tell all of your doctors about
the eye medications you are using.
Glaucoma medications can have side effects. You should notify your
ophthalmologist immediately if you think you may be experiencing
side effects.
Some eye drops may cause:
- A stinging sensation
- Red eyes Changes in pulse and heartbeat
- Changes in energy level
- Changes in breathing (especially with asthma or emphysema)
- Headaches
- Blurred vision
Pills sometimes cause:
- Tingling of fingers and toes
- Drowsiness
- Loss of appetite
- Bowel irregularities
- Kidney stones
- Anemia or easy bleeding
- Laser Surgery
- Laser surgery treatments may be effective for different types
of glaucoma. The laser is usually used in one of two ways.
In open-angle glaucoma, the drain itself is treated. The laser
is used to modify the drain (trabeculosplasty) to help control eye
pressure.
In angle-closure glaucoma, the laser creates a hole in the iris
(iridotomy) to improve the flow of aqueous fluid to the drain.
Operative surgery
When operative surgery is needed to control glaucoma, your ophthalmologist
uses miniature instruments to create a new drainage channel for
the aqueous fluid to leave the eye. The new channel helps to lower
the pressure.
Though serious complications of modern glaucoma surgery are rare,
they can occur, as with any surgery. Surgery is recommended if your
ophthalmologist feels that it is safer to operate than to allow
optic nerve damage to continue.
What is your part in treatment?
Treatment for glaucoma requires teamwork between you and your
doctor. Your ophthalmologist can prescribe treatment for glaucoma,
but only you can make sure you take your eye drops or pills.
Never stop taking or change your medications without first consulting
your ophthalmologist. Frequent eye examinations and tests are critical
to monitor your eyes for any changes. Remember, it is your vision,
and you must do your part to maintain it.
Loss of vision can be prevented
Regular medical eye exams may help prevent unnecessary vision
loss. Recommended intervals for eye exams are:
- Age 20-39: Individuals of African descent or with a family history
of glaucoma should have a medical exam every 3 to 5 years. Others
can be seen at least once during this period
- Age 40-64: Every 2 to 4 years
- Age 65 or older: Every 1 to 2 years
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