their families and friends. It provides information about open-angle glaucoma,
the most common form of glaucoma. This booklet answers questions about the cause
and symptoms of the disease and discusses diagnosis and types of
The National Eye Institute (NEI) conducts and supports research
that leads to sight-saving treatments and plays a key role in reducing visual
impairment and blindness. The NEI is part of the National Institutes of Health
(NIH), an agency of the U.S. Department of Health and Human Services.
What is glaucoma?
Glaucoma is a group of diseases that can damage the eye’s optic nerve and
result in vision loss and blindness. However, with early treatment, you can
often protect your eyes against serious vision loss.
What is the optic nerve?
The optic nerve is a bundle of more than 1 million nerve fibers. It connects
the retina to the brain. (See diagram below.) The retina is the light-sensitive
tissue at the back of the eye. A healthy optic nerve is necessary for good
In the front of the eye is a space called the anterior chamber. A clear fluid
flows continuously in and out of the chamber and nourishes nearby tissues. The
fluid leaves the chamber at the open angle where the cornea and iris meet. (See
diagram below.) When the fluid reaches the angle, it flows through a spongy
meshwork, like a drain, and leaves the eye.
Sometimes, when the fluid reaches the angle, it passes too slowly through the
meshwork drain. As the fluid builds up, the pressure inside the eye rises to a
level that may damage the optic nerve. When the optic nerve is damaged from
increased pressure, open-angle glaucoma–and vision loss–may result. That’s why
controlling pressure inside the eye is important.
Not necessarily. Increased eye pressure means you are at risk for glaucoma,
but does not mean you have the disease. A person has glaucoma only if the optic
nerve is damaged. If you have increased eye pressure but no damage to the optic
nerve, you do not have glaucoma. However, you are at risk. Follow the advice of
your eye care professional.
Not necessarily. Not every person with increased eye pressure will develop
glaucoma. Some people can tolerate higher eye pressure better than others. Also,
a certain level of eye pressure may be high for one person but normal for
Whether you develop glaucoma depends on the level of pressure your optic
nerve can tolerate without being damaged. This level is different for each
person. That’s why a comprehensive dilated eye exam is very important. It can
help your eye care professional determine what level of eye pressure is normal
Yes. Glaucoma can develop without increased eye pressure. This form of
glaucoma is called low-tension or normal-tension glaucoma. It is
not as common as open-angle glaucoma.
Who is at risk for open-angle glaucoma?
Anyone can develop glaucoma. Some people are at higher risk than others. They
- African Americans over age 40.
- Everyone over age 60, especially Mexican Americans.
- People with a family history of glaucoma.
A comprehensive dilated eye exam can reveal more risk factors, such as high
eye pressure, thinness of the cornea, and abnormal optic nerve anatomy. In some
people with certain combinations of these high-risk factors, medicines in the
form of eyedrops reduce the risk of developing glaucoma by about half.
At first, open-angle glaucoma has no symptoms. It causes no pain. Vision
As glaucoma remains untreated, people may miss objects to the side and out of
the corner of their eye. Without treatment, people with glaucoma will slowly
lose their peripheral (side) vision. They seem to be looking through a tunnel.
Over time, straight-ahead vision may decrease until no vision remains.
Glaucoma can develop in one or both eyes.
Same scene as viewed by a person with
How is glaucoma detected?
Glaucoma is detected through a comprehensive eye exam that includes:
Visual acuity test. This eye chart test measures how well you see at
A tonometer measures pressure inside the eye to detect
Visual field test. This test measures your side (peripheral) vision.
It helps your eye care professional tell if you have lost side vision, a sign of
Dilated eye exam. Drops are placed in your eyes to widen, or dilate,
the pupils. Your eye care professional uses a special magnifying lens to examine
your retina and optic nerve for signs of damage and other eye problems. After
the exam, your close-up vision may remain blurred for several hours.
Tonometry. An instrument (right) measures the pressure inside the eye.
Numbing drops may be applied to your eye for this test.
Pachymetry. A numbing drop is applied to your eye. Your eye care
professional uses an ultrasonic wave instrument to measure the thickness of your
No. There is no cure for