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What is glaucoma? Glaucoma is a disease
of the optic nerve — the part of the eye that carries the
images we see to the brain. The optic nerve is made up of
many nerve fibers, like an electric cable containing numerous
wires. When damage to the optic nerve fibers occurs, blind
spots develop. These blind spots usually go undetected until
the optic nerve is significantly damaged. If the entire nerve
is destroyed, blindness results.
Early detection and treatment by your ophthalmologist (Eye
M.D.) are the keys to preventing optic nerve damage and blindness
from glaucoma.
Glaucoma is a leading cause of blindness in the United States,
especially for older people. But loss of sight from glaucoma
can often be prevented with early treatment.
What causes glaucoma? Clear liquid called aqueous humor
circulates inside the front portion of the eye. To maintain
a healthy level of pressure within the eye, a small amount
of this fluid is produced constantly while an equal amount
flows out of the eye through a microscopic 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. 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 gets 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.
Clear liquid called aqueous humor is constantly
being produced within the eye (left). If the drainage angle
of the eye is blocked, fluid cannot flow out of the eye
(right).
What are the different types of glaucoma?
Chronic open-angle glaucoma: This is the
most common form of glaucoma in the United States.
The risk of developing chronic open-angle glaucoma increases
with age. The drainage angle of the eye becomes less efficient
over time, and pressure within the eye gradually increases,
which can damage the optic nerve. In some patients, the
optic nerve becomes sensitive even to normal eye pressure
and is at risk for damage. Treatment is necessary to prevent
further vision loss.
Typically, open-angle glaucoma has no symptoms in its early
stages and vision remains normal. As the optic nerve becomes
more damaged, blank spots begin to appear in the field of
vision. You typically won't notice these blank spots in
your day-to-day activities until the optic nerve is significantly
damaged and these spots become large. If all the optic nerve
fibers die, blindness results.
Closed-angle glaucoma: Some eyes are formed
with the iris (the colored part of the eye) too close to
the drainage angle. In these eyes, which are often small
and farsighted, the iris can be sucked into the drainage
angle and block it completely. Since the fluid cannot exit
the eye, pressure inside the eye builds rapidly and causes
an acute closed-angle attack.
Symptoms may include:
- blurred vision;
- severe eye pain;
- headache;
- rainbow-colored halos around lights
- nausea and vomiting
This is a true eye emergency. If you have any
of these symptoms, call your ophthalmologist immediately.
Unless this type of glaucoma is treated quickly, blindness
can result. Unfortunately, two-thirds of those with closed-angle
glaucoma develop it slowly without any symptoms prior to an
attack.
Who is at risk for glaucoma?Your ophthalmologist considers
many kinds of information to determine your risk for developing
the disease. The most important risk factors include:
- age;
- elevated eye pressure;
- family history of glaucoma;
- African or Spanish-American ancestry;
- farsightedness or nearsightedness;
- past eye injuries;
- thinner central corneal thickness;
- systemic health problems, including diabetes,
migraine headaches, and poor circulation.
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. Eyedrops, laser surgery and surgery
in the operating room are used to help prevent further damage.
In some cases, oral medications also may be prescribed. With
any type of glaucoma, periodic examinations are very important
to prevent vision loss. Because glaucoma can progress without
your knowledge, adjustments to your treatment may be necessary
from time to time.
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