What is a Visual Field Test?
The visual field is the entire area that can be seen when the eyes are focused on a single point. In addition to what can be seen straight ahead, the visual field includes what can be seen above, below, and to either side of the point the eyes are focused on. Vision is typically best in the middle of the visual field.
A visual field test is often given as part of an eye exam. Visual field testing helps your doctor to determine where your peripheral vision (i.e., your side vision) begins and ends, in addition to how well you can see objects in your peripheral vision.
The visual field can be tested in a few different ways, including the confrontational visual field exam, tangent screen test, and automated perimetry exam. Your doctor may perform one or a combination of these tests to examine your visual field.
Using the results of these tests, your doctor will be able to determine if you are having trouble seeing in certain areas of your visual field, as well as possible causes for these difficulties.
What Happens During the Confrontational Visual Field Exam?
The confrontational visual field exam is a basic exam performed by your eye doctor. He or she will sit or stand 3 to 4 feet in front of you. You will be instructed to cover one of your eyes using an occluder, which looks like a large spoon.
Your doctor will instruct you to stare straight ahead as he or she moves his or her hand in and out of your visual field. You will indicate when you are able to see the doctor’s hand. This test will then be repeated on the other eye.
The confrontational visual field exam only tests the outside of the visual field and is not as accurate as some of the other visual field tests. However, this test can help your doctor decide if further visual field testing is needed.
What Happens During a Tangent Screen Exam?
The tangent screen exam (also known as the Goldmann field exam) can be conducted in your eye doctor’s office. You will be seated about three feet away from a computer screen. This screen will have a target in the center for you to focus on throughout the test.
The computer will generate images on different areas of the screen. Without moving your eyes, you will tell your doctor when you are able to see objects in your side vision. Your doctor will be able to use the information collected to form a map of your visual field. This will help him or her to determine if there are certain areas in your visual field that you are not able to see. The location of these areas can help your doctor diagnose the cause of the visual field problems.
What Happens During an Automated Perimetry Test?
The automated perimetry test uses a computer program to test an individual’s visual field. You will sit and look into a dome-shaped instrument. Your doctor will instruct you to look at an object in the middle of the dome throughout the test.
There will be small flashes of light on the dome. When you see these flashes of light, you will press a button. The computer program will provide your doctor with a map of your visual field. Your doctor can then use this information to help diagnose problems or order more vision tests.
What Are the Causes of Visual Field Problems?
Visual field problems have a number of causes, including disorders that don’t originate in the eye, but in the central nervous system or the part of the brain that deals with vision.
Your doctor may use information from the visual field tests to diagnose:
- macular degeneration
- optic glioma
- brain tumor
- multiple sclerosis
- temporal arteritis
- central nervous system disorders
- hyperthyroidism (overactive thyroid)
- pituitary gland disorders
- high blood pressure
- type 1 and type 2 diabetes
Your doctor may order further eye tests to diagnose a problem. If an eye problem is not indicated as the cause of vision problems, your doctor may send you for a physical examination and blood tests.