Your visual field refers to how much you can see around you, including objects in your peripheral (side) vision. Testing your visual field is important to the health of your eyes. Visual field tests help your ophthalmologist (Eye M.D.) monitor any loss of vision and diagnose eye problems and disease.
How is a visual field test performed?
The test can be done with either a dark screen on a wall or with a large, bowl-shaped instrument called a perimeter. One of your eyes is temporarily patched during the test. Once you are seated and positioned in front the testing instrument, you are asked to look straight ahead at a fixed spot and watch for targets (spots of light) to appear in your field of vision. When you see the target, you 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.
Don’t worry about how well you are doing on the test. Obtaining accurate results is important to the health of your eyes. 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 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 visual field 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);
- brain tumors;
Visual field testing is the only way to document actual visual loss and whether the loss is progressing or remaining stable. If you are diagnosed with a particular disorder or disease, visual field tests may become a routine part of your treatment. People who have glaucoma or who are at risk for developing it take visual field tests every six months to a year to make sure their condition is stable and no vision loss has occurred.
If you have any questions about visual field testing or your vision, be sure to talk with your ophthalmologist.