Your visual field refers to how much you can see around you, including objects in your peripheral (side) vision.
Visual field testing is used to monitor peripheral, or side, vision.
This test produces a map of your field of vision. Visual field tests help your ophthalmologist monitor any loss of vision and diagnose eye problems and disease.
How is 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.
Types of visual field tests:
There are two main testing methods:
- Moving Targets. Lighted targets are moved 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 these 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 stroke.
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