Your visual field refers to how much you can see around you, including objects in your peripheral (side) vision.
This test produces a map of your complete field of vision. Visual field tests help your ophthalmologist (Eye M.D.) monitor any loss of vision and diagnose eye problems and diseases.
HOW IS A VISUAL FIELD TEST PERFORMED?
The test is performed with a large bowl- shaped instrument called a perimeter. In order to test one eye at a time, one of your eyes is temporarily patched during the test. You will be seated and positioned comfortably in front of the perimeter and asked to look straight ahead at a fixed spot (the fixation target). The computer randomly flashes points of light around the bowl-shaped perimeter. When you see a light, press the indicator button. It is very important to always keep looking straight ahead,. Do not move your eyes to look for the target, wait until it appears in your side vision. A delay in seeing a light does not necessarily mean your field of vision is damaged.
If you need to rest during the test, tell the technician and he or she will pause the test until you are ready to continue.
Your ophthalmologist will interpret the results of your test and discuss them with you.
During the visual field test, lights will appear on the screen in front of you. Press the indicator button when you see them.
These grids are results of visual field tests. The dark black shaded areas show where loss of vision has occurred.
Visual Field Test
TYPES OF VISUAL FIELD TESTS
There are two main testing methods:
Moving targets: Lighted targets are removed from where you can't see them(beyond your side vision) in towards the center of your vision until you do see them. As soon as the target appears in your field of vision, you press the indicator button.
Fixed targets: Instead of targets moving into your field of vision, fixed targets suddenly appear in different areas on the screen. When the targets appear, you press the indicator button.
WHY ARE VISUAL TESTS IMPORTANT?
Initially, visual field tests help your ophthalmologist diagnose problems with your eyes, optic nerve or brain, including:
- Loss of vision;
- Disorders of your retina (layer of cells that lines the back of your eye);
- Other neurologic conditions including brain tumors, multiple sclerosis and increased intracranial pressure.
Visual field testing is used to measure peripheral vision loss. The test is repeated at appropriate time intervals to determine if vision loss is progressing or remaining stable. If you are diagnosed with a particular disorder or disease, such as glaucoma, visual field tests become a routine part of your treatment.
If you have any questions about visual field testing or your vision, be sure to talk with your ophthalmologist.