Glaucoma Tests

Glaucoma Tests
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Glaucoma tests are a group of tests that help diagnose glaucoma, a disease of the eye that can cause vision loss and blindness. Glaucoma happens when fluid builds up in the front part of the eye. The extra fluid causes an increase in eye pressure. Increased eye pressure can damage the optic nerve. The optic nerve carries information from the eye to the brain. When the optic nerve is damaged, it can lead to serious vision problems.

There are several types of glaucoma. The main types are:

  • Open-angle glaucoma, also called primary open-angle glaucoma. This is the most common type of glaucoma. It happens when the fluid in the eye doesn’t drain properly from the eye’s drainage canals. The fluid gets backed up in the canals like a clogged sink drain that gets backed up with water. This causes an increase in eye pressure. Open-angle glaucoma develops slowly, over a period of months or years. Most people don’t have any symptoms or vision changes at first. Open-angle glaucoma usually affects both eyes at the same time.
  • Closed-angle glaucoma, also called angle-closure or narrow-angle glaucoma. This type of glaucoma isn’t common in the United States. It usually affects one eye at a time. In this type of glaucoma, drainage canals in the eyes get covered up, as if a stopper was put over a drain. Closed-angle glaucoma can be either acute or chronic.
    • Acute closed-angle glaucoma causes a rapid increase in eye pressure. It is a medical emergency. People with acute closed-angle glaucoma can lose vision in a matter of hours if the condition is not treated promptly.
    • Chronic closed-angle glaucoma develops slowly. In many cases, there are no symptoms until damage is severe.

    What are they used for?

    Glaucoma tests are used to diagnose glaucoma. If glaucoma is diagnosed early, you may be able to take steps to prevent vision loss.

    Why do I need glaucoma testing?

    If you have open-angle glaucoma, you may not have any symptoms until the disease becomes severe. So it’s important to be tested if you have certain risk factors. You may be at higher risk for glaucoma if you have a family history of glaucoma or if you are:

    • Aged 60 or older. Glaucoma is much more common in older people.
    • Hispanic and aged 60 or older. Hispanics in this age group have a higher risk of glaucoma compared with older adults with European ancestry.
    • African American. Glaucoma is the leading cause of blindness in African Americans.
    • Asian. People of Asian descent are at higher risk for getting closed-angle glaucoma.

    Closed-angle glaucoma can cause sudden and severe symptoms. If not treated promptly, it can cause blindness. Symptoms include:

    • Sudden blurring of vision
    • Severe eye pain
    • Red eyes
    • Colored halos around lights
    • Nausea and vomiting

    If you have any of these symptoms, seek medical help right away.

    What happens during a glaucoma test?

    Glaucoma is usually diagnosed with a group of tests, commonly known as a comprehensive eye exam. These exams are most often done by an ophthalmologist. An ophthalmologist is a medical doctor who specializes in eye health and in treating and preventing eye disease.

    A comprehensive eye exam includes:

    • Tonometry. In a tonometry test, you will sit in an exam chair next to a special microscope called a slit lamp. Your ophthalmologist or other health care provider will put drops in your eyes to numb them. Then you’ll rest your chin and forehead onto the slit lamp. While you are leaning into the slit lamp, your provider will use a device on your eye called a tonometer. The device measures eye pressure. You will feel a small puff of air, but it won’t hurt.
    • Pachymetry. As in a tonometry test, you’ll first get drops to numb your eye. Your provider will then use a small device on your eye called a pachymeter. This device measures the thickness of your cornea. The cornea is the eye’s outer layer that covers the iris (colored part of the eye) and the pupil. A thin cornea may put you at higher risk for getting glaucoma.
    • Perimetry, also known as a visual field test, measures your peripheral (side) vision. During perimetry, you’ll be asked to look straight ahead at a screen. A light or image will move in from one side of the screen. You’ll let the provider know when you see this light or image while still looking straight ahead.
    • Dilated eye test. In this test, your provider will put drops in your eyes that widen (dilate) your pupils. Your provider will use a device with a light and magnifying lens to look at your optic nerve and check for damage.
    • Gonioscopy. In this test, your provider will put drops in your eyes to both numb and dilate them. Then your provider will put a special hand-held contact lens on the eye. The lens has a mirror on it to let the doctor view the inside of the eye from different directions. It can show if the angle between the iris and cornea is too wide (a possible sign of open-angle glaucoma) or too narrow (a possible sign of closed-angle glaucoma).

    Will I need to do anything to prepare for a glaucoma test?

    While your eyes are dilated, your vision may be blurred and you’ll be extra sensitive to light. These effects can last for several hours and vary in severity. To protect your eyes from bright light, you should bring sunglasses to wear after the appointment. You should also make arrangements for someone to drive you home, as your vision may be too impaired for safe driving.

    Are there any risks to the tests?

    There is no risk to having glaucoma testing. Some of the tests may feel a bit uncomfortable. Also, dilation can temporarily blur your vision.

    What do the results mean?

    Your ophthalmologist will look at the results of all your glaucoma tests to figure out whether you have glaucoma. If the doctor determines you have glaucoma, he or she may recommend one or more of the following treatments:

    • Medicine to lower eye pressure or cause the eye to make less fluid. Some medicines are taken as eye drops; others are in pill form.
    • Surgery to create a new opening for fluid to leave the eye.
    • Drainage tube implant, another type of surgery. In this procedure, a flexible plastic tube is placed in the eye to help drain excess fluid.
    • Laser surgery to remove excess fluid from the eye. Laser surgery is usually done in an ophthalmologist’s office or outpatient surgery center. You may need to continue taking glaucoma medicines after laser surgery.

    If you’ve been diagnosed with glaucoma, your ophthalmologist will probably monitor your vision on a regular basis.

    Is there anything else I need to know about glaucoma tests?

    While glaucoma treatments won’t cure the disease or restore vision you have already lost, treatment can prevent additional vision loss. If diagnosed and treated early, most people with glaucoma will not have significant vision loss.

    Courtesy of MedlinePlus from the National Library of Medicine.