When to Have a Gonioscopy Eye Exam

Gonioscopy is a type of eye exam performed by an eye doctor (optometrist). It is used to check the front of the eye for glaucoma, which is a group of various conditions that can cause damage to the optic nerve. Specifically, gonioscopy examines an area called the drainage angle. It is a painless exam.

This article will detail when an ophthalmologist (a healthcare provider specializing in eye conditions) or optometrist uses gonioscopy, what happens during gonioscopy, and what you can learn from the results.

Young woman resting head on a slit lamp and having gonioscopy performed.

bluecinema / Getty Images

What Exactly Is Gonioscopy?

Gonioscopy is a test to analyze the eye's anterior chamber angle, also known as the internal drainage system. The cornea is the dome-shaped front part of your eye, and the iris is the colored part of the eye.

The anterior chamber angle is located where the cornea and iris come together. This area is important because it is where fluid from the eye drains out. Your eye has a constant production and drainage of a type of fluid called aqueous humor. If this fluid is not draining properly, it can raise the pressure in the eye and cause glaucoma. Glaucoma is a chronic eye disease that can cause vision loss or blindness if it is not treated.

Optometrists usually cannot see the anterior chamber angle, so they use a special small lens with mirrors placed on the eye surface to view the anterior chamber angle.

Reasons an Optometrist or Ophthalmologist Might Recommend It

An optometrist or ophthalmologist will use gonioscopy mainly to check for glaucoma. Gonioscopy can help determine if the drainage angle does not let fluid drain properly or if the iris is partly blocking it.


Gonioscopy may be performed if other tests during the eye exam indicate that you have glaucoma. Alternatively, it may be used as part of a routine comprehensive eye exam to confirm that there are no problems with the drainage angle. Visualizing the eye's drainage system could help the healthcare provider determine what types of treatment you need if you have glaucoma.

Gonioscopy also can be used to help treat glaucoma when combined with the use of a laser. This will help lower pressure in the eye, which can help get glaucoma under better control.

Optometrists and ophthalmologists sometimes use gonioscopy to check for other eye conditions and problems, including:

  • Eye trauma
  • Tumors
  • Uveitis (a type of inflammation in the eye's middle layer)

Procedure at a Glance

Gonioscopy is usually done at an optometrist's or ophthalmologist's office. It is a brief, non-invasive exam; it only takes about five minutes. Here's what happens during gonioscopy.

Eye Drop Preparation

You will receive eye drops that make your eyes feel numb. With these drops, you will not feel the lens that touches your eyes.

Some healthcare providers will dilate your eyes. This makes your pupils wider.

Equipment Used

Your optometrist or ophthalmologist will have you place your chin on a chin rest that is part of a special type of microscope called a slit lamp. A slit lamp helps the healthcare provider look in the eye.

While resting your chin and head on the slit lamp, you will look straight ahead.

The healthcare provider will place the gonioscopy lens with mirrors in the front of your eye while also pointing a beam of bright light into your eye. By doing these steps, they can better see your eye's drainage angle to observe how wide or narrow it is.

Is It Painful?

The exam should not cause any discomfort. Let your healthcare provider know if you feel uncomfortable.

Gonioscopy Grading and Your Results

The ophthalmologist or optometrist performing gonioscopy should be able to let you know the results right away.

They have several types of grading systems to measure results from gonioscopy. These measuring systems indicate how wide or narrow the drainage angle is. Some of the grading systems used include the Shaffer system, Spaeth system, and Scheie system. For instance, with the often-used Shaffer system, the grading ranges from 0 to 4. A 4 indicates the angle is wide open. A 0 indicates the angle is closed.

A normal drainage angle is open and does not have any blockage.

An abnormal drainage angle is narrow or closed. This indicates that the angle is fully or partially blocked.

A fully or completely blocked angle could indicate a serious and acute type of glaucoma called closed-angle glaucoma. The blocked angle could cause a sudden increase in pressure in the eye.

Other reasons for a blocked drainage angle include:

Gonioscopy Aftercare

In most instances, there is nothing special that you have to do after having gonioscopy. Follow any instructions from your optometrist or ophthalmologist.

You may be told to not rub your eyes for the first 20 minutes after having gonioscopy.

If your eyes have been dilated, it may take some time for the dilation to wear off. In this case, you may need to have someone drive you home. Your expanded pupils will be sensitive to light, so wearing sunglasses can help keep you comfortable.

Follow-Up Appointments

Make sure to keep any follow-up appointments after gonioscopy as recommended by your optometrist or ophthalmologist. These appointments can help monitor further for signs of glaucoma. If you already have glaucoma, the appointments can check to make sure that treatments are working.

Glaucoma often does not have any symptoms, but it can cause vision loss or even blindness. That is why keeping your follow-up appointments is so important.


Gonioscopy is just one type of test used to determine if someone has glaucoma. It is also sometimes used during a comprehensive eye exam. Gonioscopy is a painless exam to check how wide or narrow the drainage angle in your eye is. An optometrist or ophthalmologist uses gonioscopy when a person has or may have glaucoma. The test takes about five minutes, and the results can help determine if you have glaucoma.

A Word From Verywell

Some people worry about going to the optometrist or ophthalmologist, especially when their eyes need to be dilated. It may help to keep in mind that gonioscopy is a quick and painless procedure. Avoiding your healthcare provider is not worth the risk of potentially having untreated glaucoma.

Frequently Asked Questions

  • Does insurance cover gonioscopy?

    Insurance may cover gonioscopy. Check with your insurance provider to verify this, or ask your healthcare provider's office for guidance.

  • Is there any discomfort during a gonioscopy exam?

    You shouldn't feel any discomfort. You may feel some stinging when the eye drops are inserted into your eye. The numbing drops should stop you from feeling anything, although you may feel the lens touching your eyelashes.

  • How do you improve eye drainage naturally?

    There is not a proven way to improve eye drainage naturally. Regular eye exams as recommended by your optometrist or ophthalmologist, physical activity, and eye protection during sports or home improvement can help prevent glaucoma.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Glaucoma Research Foundation. Gonioscopy: what is it and why is it needed?

  2. American Academy of Ophthalmology. What is gonioscopy?

  3. MyHealth.Alberta.Ca. Gonioscopy.

  4. American Academy of Ophthalmology. Gonioscopic grading systems.

By Vanessa Caceres
Vanessa Caceres is a nationally published health journalist with over 15 years of experience covering medical topics including eye health, cardiology, and more.