Glaucoma Tests

What are glaucoma tests?

Glaucoma includes a group of eye problems that can damage your optic nerve. If a healthcare provider suspects you have glaucoma, you might need certain tests like:

• Eye angle exam.
• Corneal thickness measurement.
• Dilated eye exam.
• Eye pressure check.
• Optic nerve imaging.
• Visual field test.

What is glaucoma?

Glaucoma is a term that includes several types of eye disorders that cause damage to your optic nerve. The condition is usually caused by increased pressure in your eye. It often worsens over time and can cause vision loss or blindness.

The optic nerve sends signals from your retina to your brain. Your retina is a layer of tissue in the back of each eye that senses light. The information goes from your retina to your optic nerve to your brain, which creates the images you see.

Who is at increased risk for developing glaucoma?

A family history of glaucoma significantly increases your lifetime risk of developing the condition. You may have higher risk if you:

• Are Black (open-angle glaucoma).
• Have ancestors from East Asia (closed-angle glaucoma).
• Have a history of farsightedness (closed-angle glaucoma)
• Have had an eye injury or complicated eye surgery.
• Have diabetes.
• Have high blood pressure (hypertension).
• Have been taking corticosteroid medicines (like prednisone).
• Are older than 40.

When would a glaucoma test (screening exam) be needed?

You may need an eye exam that includes glaucoma tests if you’re experiencing problems with your vision like:

• Blind spots.
• Blurry vision.
• Eye pain or pressure.
• Headaches.
• Rainbow circles when you look at lights.
• Red eyes.
• Tunnel vision.

The American Academy of Ophthalmology (AAO) also suggests that people who are at risk for glaucoma have complete eye exams according to the following schedule:

• Ages 40 to 54, every one to three years.
• Ages 55 to 64, every one to two years.
• Ages 65 and older, every six to 12 months.

Who performs glaucoma tests?

An ophthalmologist performs tests for glaucoma. This type of physician specializes in preventing, diagnosing and treating eye disorders.

How does glaucoma testing work?

Glaucoma testing may involve one test or a combination of tests. The procedures are quick, painless and noninvasive. They help ophthalmologists see inside your eyes, assess vision loss and choose treatments.

Glaucoma tests include:

Angle exam

This test shows the angle where your cornea (the clear outer layer of your eye) meets your iris (the colored part of your eye). Your eye’s drainage system is in this angle.

Your ophthalmologist uses eye drops to numb your eye, then touches your cornea with a special lens. The lens shows whether the angle is open or closed. If the angle is closed, the drainage system is blocked, which may indicate glaucoma. The test is also called gonioscopy.

Corneal thickness measurement

This test measures the thickness of your cornea, which helps your eye doctor determine your risk for glaucoma. Your ophthalmologist numbs your eye with drops, then touches your eye with a small probe. The test is also called pachymetry.

Dilated eye exam

This test uses eye drops to open (dilate) your pupil (the black circle at the center of your eye). A special tool shines a bright light into the back of your eye and magnifies your retina and optic nerve. This helps your ophthalmologist see your retina and optic nerve, including color, size, shape and blood vessels. Your ophthalmologist may then be able to estimate whether or not there’s damage to your optic nerve, and if this is from glaucoma.

Eye pressure check

Increased pressure in your eye is one of the most important signs of glaucoma. For an eye pressure test, your ophthalmologist uses eye drops to numb the surface of your eye. Then they use a tiny instrument to touch the surface of your eye and flatten the cornea, which measures the pressure.

An eye pressure check doesn’t hurt, and it takes only a few minutes. But you must remain relaxed and still during the test. This test is also called tonometry or applanation.

Optic nerve imaging

This test takes pictures of your retina and optic nerve. Your ophthalmologist dilates your pupils, then uses a special digital camera to capture images.

Many ophthalmologists use a special machine called optical coherence tomography. You rest your chin on a machine and look into a lens. Nothing touches your eye, and the machine takes pictures for a minute or two. The images show each layer of eye tissue and map the area.

Visual field test

This test helps determine whether you’ve lost sight in specific areas (for example, straight ahead or to the side). Visual field testing can also show how severe glaucoma is. Multiple tests may be used over time in glaucoma to determine how quickly it’s progressing.

Your ophthalmologist asks you to look at an object straight ahead, such as their nose. They may ask you to cover one eye at a time. Then they ask you to report whether you can see something along the side of your vision while still looking straight ahead.

An ophthalmologist may use certain tools for visual testing. For example, automated static perimetry requires you to look into a machine and track lights. Another method involves looking at a pattern of lines and reporting whether any areas look blurry or blank.

What can I expect after a glaucoma test?

After glaucoma testing, you may have certain restrictions. For example, your vision will probably be blurry, so you should have someone else drive you home. If you had a dilated eye exam, you may need to wear sunglasses to protect your eyes from excess light and ultraviolet (UV) rays.

Your ophthalmologist gives you detailed instructions, depending on the type of tests you have.

What are the risks of glaucoma tests?

Glaucoma tests are safe and don’t involve any risks. Your vision may be blurry or overly sensitive after testing, but it gets better throughout the day.

When will I know the results of glaucoma tests?

Most glaucoma test results are available immediately during the same appointment.

What do glaucoma test results mean?

Your ophthalmologist will discuss the test results with you and what they mean. Your doctor will consider findings from all tests performed to determine if you’re at risk for glaucoma, or if you have the condition and what type you have.

Results outside the normal healthy range may indicate glaucoma or the need for further testing. Abnormal test results may include:

• Angle exam (gonioscopy): Narrow or blocked drainage angle (the area where your eye fluid drains).
• Corneal thickness measurement (pachymetry): A thin cornea, which increases your risk of primary open-angle glaucoma.
• Dilated eye exam: Atypical size and shape of blood vessels inside your eye.
• Eye pressure check: Intraocular (eye) pressure greater than 22 mmHg (millimeters of Mercury).
• Optic nerve imaging: Unusual findings like swelling or buckling of the optic nerve or a bumpy retina.
• Visual field test: The presence of specific spots where your vision goes blank or gets blurry.

What happens if I have glaucoma?

Your doctor will recommend the next steps. They may suggest follow-up appointments to check your vision regularly. Or they might recommend glaucoma treatments like:

• Medications to reduce pressure in your eyes — either eye drops or pills.
• Surgery to create an opening in your eye so extra fluid can drain away and reduce eye pressure.
• Surgery to implant tubes that drain excess fluid.
• Laser treatment to help drain fluid.

How can I cope with vision loss?

You can slow the progression of glaucoma and treat it, especially if you catch it early. In addition to any treatments your ophthalmologist recommends, there are several steps you can take to cope with vision loss.

A note from Cleveland Clinic

Glaucoma tests can determine whether your optic nerve is damaged, which can affect your vision. Your ophthalmologist may use one or more tests to check for glaucoma and recommend treatment. You can have glaucoma without any symptoms until the later stages. It’s important to get regular eye exams to detect problems before vision loss occurs.