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Visual field tests measure a person’s entire field of vision, including peripheral vision, and can detect blind spots and eye diseases. Different types of tests include automated perimetry, rate doubling perimetry, electroethinogram, and comparison.
A visual field test measures a person’s entire field of vision. This includes both central and peripheral, or side, vision. These tests map individual fields of the eyes. Visual field testing requires the patient’s full cooperation, as they must understand the test that is to be performed and participate in the entire test so that the patient has a thorough understanding of her condition.
An eye exam that isn’t as thorough as a visual field test may not measure peripheral vision. Peripheral vision is the full horizontal and vertical range of what a person can see. Commonly called lateral vision, it is that part of the vision that a patient sees not directly but from the corners of her eyes.
The purpose of a visual field test is to detect blind spots, which can indicate eye disease. Eye diseases include damage to the optic nerve, optic neuropathy, retinal disease, drooping eyes, toxic exposure, and damage to the inner lid of the eye, caused by overexposure to light. A visual field test of the eye can also detect abnormalities in the brain that cause strokes or tumors. These abnormalities not only affect the visual field, but the location of the stroke or tumor is often determined by the size, shape, and location of the eye problem or defect.
A visual field test is performed by the patient covering one eye and looking straight ahead at a target object. Central vision and peripheral vision are tested individually. Doctors test a person’s central vision by focusing on a part of the face, such as an eye or ear. To test peripheral vision, the patient also fixates on an object, but is asked to describe what can be seen from the corners of his or her eyes.
Types of visual field tests include automated perimetry, rate doubling perimetry, electroethinogram, and comparison. Automated perimetry allows the patient to fixate on a light source so that response to the presence of objects can be tested in different viewing areas of the field. Frequency doubling perimetry involves the use of colored vertical bars for flicker at high frequencies. If the patient cannot see the bars, damage to the optic nerve may be present.
An EEG measures how a patient responds to flashing stimuli, and the electrode can detect how sensitive the retina is. An overly sensitive retina can be a sign of an eye disease. The last major type of visual field test is a conflict test. This tests peripheral vision by moving an object around a patient’s peripheral vision frame to test the speed of response.
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