The visual field is the entire area you can see when your eyes are focusing on one central point. If you’ve been to an eye doctor, you’ve most likely had a visual field test. A visual field test is an eye exam used to check for blind spots or peripheral vision loss. It determines if the patient has lost any vision in the side, upper or lower areas of their visual field.
Visual field testing is an important part of regular eye care, especially for individuals who are at high risk of eye diseases and other issues. People with certain medical conditions, such as diabetes or high blood pressure, are more likely to develop issues with the blood vessels in the optic nerve and retina. Visual field testing helps your doctor spot early signs of these conditions that damage vision gradually.
Types of visual field testing
There are several types of visual field tests. The type of visual field test you will need depends on your eye health and vision.
Confrontation visual field test
During a confrontation visual field test, your doctor will ask you to cover one eye and look at an object directly in front of you. Your doctor will then hold up an object or different numbers of fingers off to each side. While you continue to look directly in front of you, you will say how many fingers you see or if you see the object as the test is assessing your periphery or side vision.
Automated static perimetry test
This type of test uses a computer to create a detailed map of your visual field. It is useful for diagnosing specific ocular conditions or monitoring the progress of an ocular disease over time.
During an automated static perimetry test, you will sit in front of a bowl-shaped device called a perimeter. Each eye will be tested separately. Your doctor will ask you to look straight ahead and press a button whenever you see lights flashing in different areas of the bowl. The instrument records which lights you saw and didn’t see and prints out the results for your doctor to review.
Kinetic visual field test
This type of visual field test is like the automated static perimetry test, except it uses moving light targets instead of flashing lights.
Frequency doubling perimetry
The frequency doubling perimetry test uses an optical illusion to detect vision loss. During the test, black and white lines will appear on a perimeter screen and flicker at varying rates. If you can’t see the lines clearly throughout the test, you may have vision loss in parts of your visual field.
Another way your optometrist can assess loss of vision is a test called electroretinography. During this test, your doctor will give you eye drops to dilate your pupils and other anesthetic drops to prevent discomfort. They will then use a speculum to hold open your eyelids and place a tiny electrode on the cornea (the front surface of the eye). You will then look at flashing lights in the perimeter, and the electrode will record your eye’s response to the flashing lights.
The Amsler grid test checks for diseases that impact your central vision, including macular degeneration. This test is a pattern of straight lines which make a grid of many equal squares. Your doctor will ask you to look at a dot in the center of the grid and describe any areas that may appear wavy, blurry, or blank.