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  • What Is Gonioscopy?

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    Reviewed By J Kevin McKinney, MD
    Mar. 27, 2019

    Gonioscopy is a painless exam your ophthalmologist uses to check a part of your eye called the drainage angle. This area is at the front of your eye between the iris and the cornea. It is where fluid called aqueous humor naturally drains out of your eye. Your ophthalmologist will perform a gonioscopy to check to see if this drainage angle is functioning properly.

    Gonioscopy: What To Expect

    For a gonioscopy exam, you will rest your head in the chin holder of a slit-lamp microscope (the special instrument your ophthalmologist uses to look in your eyes). At this point, your eyes will have been numbed with eye drops.

    Your ophthalmologist will place a special contact lens with mirrors directly on your eye. They will shine a beam of light into the lens to highlight the drainage angle. The lens mirrors help to show this part of the eye that is essentially around a corner inside the eye and difficult to see.

    You may feel the lens touch your eyelashes, but typically a gonioscopy is not painful in any way. This exam usually takes just a few minutes.

    What Is Gonioscopy Used For?

    Our eyes constantly make aqueous humor. As new aqueous flows into your eye, about the same amount should leave the eye through the drainage angle. This process keeps pressure in your eye (called intraocular pressure or IOP) stable. If the drainage angle is not working properly, fluid builds up. Pressure in the eye rises, damaging the optic nerve. This is often how glaucoma develops.

    Your ophthalmologist will perform a gonioscopy if certain conditions are found during your eye exam. Most commonly, gonioscopy is done to check for signs of glaucoma. The exam can show if your drainage angle is too narrow for fluid to drain properly, or if it is blocked by part of the iris.

    In other cases, gonioscopy may be done when there are signs of uveitis, eye traumatumors or other conditions.

    When Should You Have a Gonioscopy?

    Early signs of vision changes and eye disease may begin around age 40. This is when all adults should get a baseline eye disease screening with an ophthalmologist.

    Screening for signs of glaucoma, your ophthalmologist will perform a gonioscopy to check the appearance and function of your drainage angle. Some people are considered glaucoma suspects. They may or may not have higher than normal eye pressure, but their ophthalmologist may notice other signs that glaucoma could develop. In this case, the ophthalmologist will want to do a gonioscopy and other glaucoma screenings regularly to check for changes over time.

    Time is of the essence when it comes to monitoring your eyesight. It is important to keep your scheduled appointments with your ophthalmologist. Regular exams can save your vision.