This is a test to measure your peripheral vision. There are many ways to check side vision, but when we say we’re going to get a “visual field” we are usually talking about the Humphrey Visual Field. This is a computer-controlled machine that maps out peripheral vision in an objective and precise manner. You wear an eye patch over one eye and sit forward in a bowl of light. While you stare straight ahead at a fixed point, the computer shines a spot of light in various places in your peripheral vision. Every time you see the light, you click the buzzer and the computer maps this data for us. Visual fields are very useful for detecting vision loss in patients with glaucoma. Because a third of the brain is devoted to the visual pathway (and processing of visual images), neurologic problems can be detected and localized with a visual field as well.