The visual field test measures your peripheral vision, also called your side vision. Many diseases can reduce your peripheral vision. To diagnose and treat these conditions, we must carefully measure the peripheral vision. Your peripheral vision is measured with a special test called a visual field test.

Taking a visual field test can be challenging, and the results are only useful if you can perform the test well. Each eye will be tested separately, and the eye not being tested will be covered with an eye patch. To get started, your head will be comfortably positioned in the visual field machine. The test takes five to ten minutes per eye and, if you are uncomfortable, you will not be able to do a good job taking the test. If you are not comfortable, tell your technician so you can be adjusted until you’re comfortable.

Once you are comfortably positioned, you will be looking into a dimly lit bowl. Your technician will ask you to stare at a small target light in the middle of the bowl. Your job is to keep staring at that spot throughout the whole test. You may blink your eyes whenever you need to—this will not affect the test.

Before the test begins, you will be handed a small device with a button on it. Try pushing the button a few times before starting the test. If you have arthritis or any other health problem that makes it hard for you to push the button in your hand, now is the time to tell your technician.

During the test, small lights will appear throughout the bowl. Your job is to push the button every time you see one of the lights. Pushing the button is how the machine knows you saw that light. If you see a light but don’t push the button, the machine will think you did not see that light. Don’t worry about missing lights when you blink—the machine will come back to each spot you missed and check it again.

You should keep looking straight at your small target even when you see the test lights in your peripheral vision—if you move your eyes to look at them, the test is no longer measuring your peripheral vision. The machine keeps track of whether you look around or not, and if you look around too much, your doctor may not be able to use your test results and you may have to repeat the entire test.

You may hear some sounds during the test. The machine makes noises while the test is performed. If you hear noises but do not see lights, don’t worry—sometimes the machine shines lights too small or too dim to be seen, or doesn’t shine any lights at all, just to make sure you aren’t hitting the button every time you hear the noise. If you hit the button even when you don’t see the light, your test results may not be useful and you may need to repeat the test.

When the test is complete, the machine will print out a map of your peripheral vision. The pattern of this map tells your doctor where you can see and where you can’t see.