Test Overview
Gonioscopy is an eye examination to
look at the front part of your eye (anterior chamber) between the
cornea and the
iris.
Gonioscopy is a painless examination
to see whether the area where fluid drains out of your eye (called the
drainage angle) is open or closed. It is often done
during a regular eye examination, depending on your age and whether you are at
high risk for glaucoma.
Gonioscopy is done if your
doctor thinks you should be checked for
glaucoma. Glaucoma is an eye disease that can cause blindness by damaging the
optic nerve. If you have glaucoma, gonioscopy can help
your eye doctor see which type of glaucoma you have.
Why It Is Done
Gonioscopy is done to:
- Look at the front of the eye to check for
glaucoma.
- See if the
drainage angle of the eye is closed or nearly closed. This helps your doctor see
which type of glaucoma you have. Gonioscopy can also find scarring or other
damage to the drainage angle.
- Treat glaucoma. During gonioscopy,
laser light can be pointed through a special lens at
the drainage angle. Laser treatment can decrease pressure in the eye and help
control glaucoma.
- Check for birth defects that may cause
glaucoma.
How To Prepare
If you wear contact lenses, remove them
before this test and do not put them back in for 1 hour after the test or
until the medicine used to numb your eye wears off.
If your eyes
might be dilated during your examination, your doctor may suggest that you arrange for someone to
drive you home after the test.
How It Is Done
Gonioscopy is usually done by a doctor
who treats eye problems (ophthalmologist).
Eyedrops are used to
numb your eye so that you will not feel the lens touching your eye during this
painless examination.
Gonioscopy is usually done in your doctor's
office. During gonioscopy, you may be asked to lie down or to sit in a chair. A
microscope (slit lamp) is used to look inside your eye. If you sit, you will
place your chin on a chin rest and your forehead against a support bar and look
straight ahead. A special lens is placed lightly on the front of your eye, and
a narrow beam of bright light is pointed into your eye. Your doctor looks
through the slit lamp at the width of the drainage angle.
The
examination takes less than 5 minutes.
How It Feels
Gonioscopy does not usually cause any
discomfort. The eyedrops used to numb your eye may burn a little. You may find
it hard to keep from blinking during the test.
Risks
If your pupils were dilated, your vision may be
blurred for several hours after the test. You should not rub your eyes for 20
minutes after the test, or until the medicine wears off.
There is
also a very small risk of an eye infection or an
allergic reaction to the eyedrops used to numb your
eyes.
Results
Gonioscopy is an eye examination to look
at the front part of your eye (anterior chamber) between the
cornea and the
iris. During gonioscopy, the drainage angle of your
eye is checked. Your doctor measures the drainage angle, its width, and checks
whether it is open or closed.
Gonioscopy results| Normal: | The drainage angle
appears normal, is wide open, and is not blocked. |
|---|
| Abnormal: | The drainage angle looks narrow, is a slit, or is closed. This means that the angle is partially or completely blocked, or there's a risk that the angle will close in the future. |
|---|
A partially or completely blocked drainage angle may mean that you have closed-angle glaucoma. There are many reasons that a drainage angle can be blocked. These include scar tissue, abnormal blood vessels, injury or infection, and extra color pigment of the iris.
What Affects the Test
Reasons you may not be able to
have the test or why the results may not be helpful include:
- You cannot sit or lie still during the
test.
- You have an allergy to the medicine used to numb your eye
during the test.
What To Think About
Other tests may be done to check
for glaucoma or other eye problems. These tests include a slit lamp
examination, tonometry (which measures the pressure inside the eyeball),
ophthalmoscopy (which checks the optic nerve), and perimetry (which tests side
vision).
To learn more, see:
Credits
ByHealthwise Staff
Primary Medical ReviewerAdam Husney, MD - Family Medicine
E. Gregory Thompson, MD - Internal Medicine
Kathleen Romito, MD - Family Medicine
Specialist Medical ReviewerChristopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology
Current as ofMay 17, 2017