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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. See a picture of the eyeClick here to see an illustration..

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 developing glaucoma.

Gonioscopy is done if your doctor (ophthalmologist) 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 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 angleClick here to see an illustration. 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 one hour after the test or until the medicine used to numb your eye wears off.

If your eyes might be dilated during your examination, you should 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:

Most people with open-angle glaucoma have a large, open drainage angle. The drainage angle may be blocked so fluid does not drain from the eye.

Scar tissue or other damage to the drainage angle is seen.

Most people with closed-angle glaucoma have a drainage angle that is partially or completely blocked by the iris. Closed-angle glaucoma blocks the movement of fluid between the chambers of the eye.

Other conditions that can cause glaucoma—such as an eye injury, an eye infection, breakdown and flaking off of the color pigment of the iris, or a form of closed-angle glaucoma called plateau iris syndrome—may be seen.

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). For more information, see the topics Slit Lamp Examination, Tonometry, Ophthalmoscopy, and Vision Testing.

Credits

ByHealthwise Staff
Primary Medical ReviewerKathleen Romito, MD - Family Medicine
Specialist Medical ReviewerChristopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology
Last RevisedApril 6, 2010

eMedicineHealth Medical Reference from Healthwise

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