Visual Field Test
A visual field test measures your peripheral vision, or how well you can see above, below and to the sides of something you’re looking at. It’s also called a perimetry test. Visual field testing is important for many conditions, including glaucoma.
What is a visual field test?
A visual field test is a simple and painless test an eye care provider gives you to diagnose or monitor various eye conditions.
A visual field test measures two things:
How far up, down, left and right your eye sees without moving (when you’re looking straight ahead).
How sensitive your vision is in different parts of the visual field, which is the name for the entire area that you can see.
Your eyes normally see a wide area of the space in front of you. Without moving your eyes, you can see not only what’s straight ahead, but also some of what’s above, below and off to either side. Providers call all of the area you can see that isn’t right in front of you “peripheral vision.” This surrounds the area that’s right in front of you that you can see (central vision).
Vision is usually best right in the middle of the visual field, so you probably turn your eyes toward the things you want to see more clearly. The farther away from the center of your vision an object is, the less clearly you can see it. When an object moves far enough to the side, it disappears from your vision completely.
When is a visual field test performed?
When you visit an optometrist or ophthalmologist, a visual field test is part of a routine eye exam. Visual field testing can help your eye care provider find early signs of diseases like glaucoma that gradually damage vision. Some people with glaucoma don’t notice any problems with their vision, but the visual field test shows a loss of peripheral vision.
A visual field test can also help your provider find out more about the part of your nervous system that allows you to see. The visual part of your nervous system includes:
Your retina, the part of your eye that’s like a translator that changes light energy into an electrical signal.
Your optic nerve, the nerve that carries the signals to your brain so they can become images.
Your brain, the place where the signals become the images you see.
Issues with any part of this system can change your visual field. There are well-known patterns in the test results that help providers recognize certain types of injury or disease.
By repeating visual field tests at regular intervals, providers also can tell whether your condition is getting better or worse.
Medical conditions that might cause a provider to order a visual field test
Your healthcare provider may want you to have a visual field test if you have (or they think you may have) certain conditions. Providers use the results to both diagnose and monitor conditions such as:
Multiple sclerosis (MS).
Blind spot (scotoma).
Why do some people need to have visual field tests many times?
Sometimes your eye care provider will want to repeat the visual field test right away to make sure the results are accurate. If you’re tired, for example, the test results can be unreliable.
Your provider might also recommend that you take a visual field test again in a few weeks, a few months or a year. This might be necessary to make sure that they find any new problems early. When you have certain eye conditions, your provider will do visual field tests regularly to find out how well the treatment is working.
Visual field tests are especially important in the treatment of glaucoma. These tests will tell the provider if you’re losing vision even before you notice. That’s just one of the reasons why people who have glaucoma should keep all of their appointments with their provider.
What happens during a visual field test?
You don’t have to prepare for a visual field test. It’s not invasive, so you aren’t likely to have any side effects.
There are several types of visual field tests, but they all have one thing in common: you look straight ahead at one point and signal when you see an object or a light somewhere off to the side.
Your provider will explain to you exactly where to look so that the test is accurate.
The two most basic types of visual field tests are very simple:
Amsler grid: The Amsler grid is a pattern of straight lines that make perfect squares. You look at a large dot in the middle of the grid and describe any areas where the lines look blurry, wavy or broken. The Amsler grid is a quick test that only measures the middle of the visual field (your central vision) and provides your doctor with a small amount of information.
Confrontation visual field: The term “confrontation” in this test just means that the person giving the test sits facing the person having the test, about 3 or 4 feet (around 1 meter) away. The provider holds their arms straight out to the sides. You look straight ahead, and the tester moves one hand and then the other inward toward you. You give a signal as soon as you see their hand.
The confrontation visual field test measures only the outer edge of the visual field. It’s not very exact.
Other types of visual field tests
You may hear about different types of or terms for visual field tests, including static and kinetic perimetry tests. (Perimetry test is another way of saying peripheral vision test.)
Kinetic perimetry tests: A kinetic perimetry test is one in which the person giving the test moves an object around, and you tell them when you can see it. Providers often use the Goldmann perimetry test.
Static perimetry tests: Automated peripheral vision tests are static perimetry tests. You look into a bowl-shaped machine and respond by pressing buttons when you see the object. Common types of static tests are the Humphrey and the Octopus.
How long does a visual field test take?
A test usually isn’t longer than about five to 10 minutes per eye.
What kind of visual field tests give more detailed information?
Computerized instruments are available to perform visual field tests and calculate results. These instruments give more reproducible and accurate results because:
Your head is always in the same place during the test.
The instrument has a large central “target” for you to look at, so the center of the visual field stays steady.
The instrument uses tiny spots of light to test vision. The provider can change the brightness and color of the light to measure the sensitivity of vision at each location.
There are clear standards for “normal” results. The instrument can compare each new test to these standards.
What do the results of the visual field test mean?
A “normal” visual field test means that you can see about as well as people without vision issues.
The visual field test shows the amount of vision loss and the affected areas. The instrument prints the results as patterns of dots or numbers. The patterns tell your provider how well your eyes and visual field system work. This helps your provider diagnose an underlying health condition and what treatment you need.
A test that shows visual field loss means that vision in some areas isn’t as keen as it should be. A test could show that you have a small area of lost vision, or all vision lost in large areas.
When should I know the results of the test?
Generally, your provider should be able to give you results right away.
What are the next steps if the results are abnormal?
Abnormal results may mean different things. These results can indicate different types of issues, including glaucoma, macular degeneration or stroke. The follow-up will vary.
Your eye care provider will discuss treatment options with you.
When should I call my provider?
You should always contact your eye care provider if you have any new vision loss or eye discomfort. If you have sudden vision loss or eye pain, go to an emergency room for immediate medical help.
It’s a good idea to get regular eye exams. Part of your exam will include visual field testing to find out how well you can see above, below and to each side of the object you’re looking directly at. If there are issues with your visual field, your provider can use the results to help diagnose medical conditions you might have or to monitor how well treatment is working for an existing condition.