Gonioscopy
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.
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Normal: |
The drainage angle appears normal, is wide open, and is not blocked. |
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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:
Current as of: May 5, 2019
Author: Healthwise Staff
Medical Review:Adam Husney, MD – Family Medicine & E. Gregory Thompson, MD – Internal Medicine & Kathleen Romito, MD – Family Medicine & Christopher Joseph Rudnisky, MD, MPH, FRCSC – Ophthalmology
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