Visual Field is an important test that can detect dysfunction in the central and peripheral vision which can be caused by various medical conditions. Such as Glaucoma, Stroke, Brain tumors or other neurological defects. During the test there is a center fixation light and blinking test lights in your peripheral vision. When you see a light blink, click the button to let the machine know that you saw it. Following the lights away from the fixation point decreases the reliability of the test and the ability of your doctor to monitor your disease.