Visual field testing is conducted to determine if there are any blind spots in vision, and if so, where the blind spots are. The size and shape of the blind spot, otherwise known as scotoma, can show how an eye disease, such as glaucoma, or a brain disorder is affecting vision.
Visual field testing is an important part of comprehensive eye care, especially for people who are at risk of developing eye diseases which result in vision loss. People who have diabetes, high blood pressure, or both, have a greater risk of developing issues with blood vessels in the optic nerve and retina, and need visual field testing to monitor effects on their vision.
There are six types of visual field testing.
Confrontation visual field test
During a confrontation visual field test, your doctor will ask you to look at an object directly in front of you while one of your eyes is covered. Your doctor may then have an object or hold up different numbers of fingers off to the side and ask you to tell them what you can see in your peripheral vision as you continue looking at the target straight ahead of you.
Automated static perimetry test
This type of visual field test will create a detailed map of your visual field. It is used to obtain a more specific diagnosis of an ocular condition or to monitor the progress of an ocular disease.
During an automated static perimetry test, you will be seated in front of a bowl-shaped device called a perimeter. The test will be run separately on each eye. The doctor will ask you to keep your eye on the target in the center throughout the test. You’ll see lights flashing in different areas of the bowl. When lights flash, you’ll press a button. Any lights for which you did not press a button due to not seeing them will be added up at the end of the test and printed out for your doctor to review.
Kinetic visual field test
This type of visual field test is like the automated static perimetry test, with one key difference: the lights will be moving instead of flashing.
Frequency doubling perimetry
The frequency doubling perimetry test utilizes an optical illusion to detect loss of vision. During this test, black and white lines are displayed on a perimeter screen. The lines will then flicker at different times and rates. If you find you cannot see the lines clearly throughout the test, there may be some vision loss in parts of the visual field.
During this test, your doctor will administer eye drops to dilate and numb your eyes. A speculum will then be used to hold your eyes open, and a tiny electrode will be placed on the cornea, the front surface of the eye. You will then look at flashing lights in the perimeter device, and the electrode will measure your eye’s response to the flashing lights.
This type of visual field testing is used for people with age-related macular degeneration. The Amsler grid is a series of straight lines which make a grid of equal squares. You’ll be asked to look at the dot in the middle of the grid and describe any areas that are wavy, blurry, or blank.