Visual field testing defines the severity and shape of defects in both central and peripheral vision. Various techniques may be used, ranging from simple tests to more complicated ones that require special instruments.
Confrontation (or kinetic perimetry) brings a test object from a non-seeing area (such as behind the head) into the field of vision. You will be asked to focus your eyes on a central point—such as the examiner’s nose, the center of a dark screen (known as a "tangent screen"), or the center of a 2-foot bowl-shaped instrument called a perimeter—and to tell the examiner when you first see the object enter your visual field. Depending on the technique, different test objects are used (for example, the examiner’s fingers, a pencil, or different-sized spots projected on the perimeter).
Static perimetry uses a different type of bowl-shaped perimeter in which computer-driven programs cause spots of light to appear at multiple points. You are asked to press a button when you see a light.
Color testing assesses your ability to recognize the color of test objects, red being especially important for identifying neurologic (nerve) disorders. The techniques of kinetic perimetry are employed, but with colored objects or lights.
Purpose of the Visual Field Testing
- To detect patterns of vision loss that indicate specific disorders, including diseases of the retina and optic nerve, glaucoma, brain tumors, and stroke
- To monitor the course of visual field loss over time and the effectiveness of treatment for disorders such as glaucoma, optic neuritis (inflammation of the optic nerve), and brain tumors
- To record the level of peripheral vision
- To record actual visual loss; to identify if it is getting worse or remaining the same
Who Performs It
- An ophthalmologist or a trained technician
- The simpler visual field tests (such as confrontation testing using the examiner’s fingers as test objects) are used for people with decreased mental function due to a stroke, head injury, brain tumor, or infection. More complicated techniques (such as static perimetry) require a high level of alertness and sustained attention.
Before the Visual Field Testing
- No special preparation is needed.
What You Experience
- One eye is first covered with a patch.
- You are instructed to indicate when you see a test object in your visual field. The exact procedure varies depending on which technique is performed.
- The test is repeated in the other eye.
- The procedure takes about 30 minutes.
Risks and Complications
After the Visual Field Testing
- You may resume your normal activities.
- An ophthalmologist reviews the data for evidence of a visual field defect. Certain diseases produce characteristic patterns of visual loss.
- The doctor considers these findings along with your symptoms, your eye exam, and the results of other tests to decide on the need for further testing, such as a brain CT scan or MRI, or treatment.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media