Your complete visual field is the entire area seen when your gaze is fixed in one direction. The complete visual field is seen by both eyes simultaneously, and it includes the central visual field (which detects the highest degree of detail) and the peripheral (side) visual fields. Visual field screening monitors and gives the doctor very important information about the neurological function of the retina, optic nerve, and brain. This test is usually ordered to monitor certain eye diseases such as glaucoma, and also as a screening test prior to surgery.
Visual field tests can help detect eye diseases or nervous system problems that limit your ability to see objects clearly in the entire visual field or in one part of it. Visual field tests come in different forms, but most have a white bowl with a small fixation light in the center. The most sophisticated ones are computerized. After your pupils have been dilated, you will be comfortably seated in front of the instrument. The trick to the test is to stare straight ahead as lights flash in the periphery. A button is available to press each time a light appears. A technician is available throughout the test should you have a question or need to pause for a break.
Afterward, the computer analyzes the data and prints a chart of the results. Your visual field results are organized in your record so that your doctor can monitor your progress. Several tests are commonly done to evaluate a person’s visual field.
Visual Field Screening Tests
Confrontation Test – This is a simple screening method that allows the health professional to estimate your visual field. You will be asked to stare at a specific point while your health professional moves an object (such as a finger) within your visual field.
Perimetry Test – This test identifies defects in your visual field (usually of one eye at a time) by having you sit in front of a machine that flashes lights randomly at various points in the visual field. Alternatively, your health professional may move objects toward your central vision and note at what point you see them.
Tangent Screen Test – Tangent screen is a form of perimetry that helps identify defects in the visual field by determining where a white target object can be seen against a black background.
Amsler Grid Test – This is a simple screening test for macular degeneration, a disease that causes the loss of vision in the central area of the visual field. You are asked to focus on a small area with grid lines that form boxes. Distortions or defects in the lines suggest retinal damage or fluid under the retina.
For more information about vision problems or to determine if you would benefit from vision therapy, please schedule an appointment with Dr. Cantrup.