The area in space that may be visualized by the eye is known as the visual field. Plotting of the visual field is important for many disorders, particularly disorders of the retina, optic nerve and brain. This would include retinal dystrophies, glaucoma, strokes and brain tumors. Patients often incorrectly assume that because they can see their hand waving off in the periphery their peripheral vision is fine. However, testing peripheral vision with such a gross test is usually only useful for the most severe losses of peripheral vision, as sometimes occurs in strokes. The much more common and subtle vision deficits may only be detected by the sophisticated methodology of a computerized visual field analyzer, such as the Octopus 101 or Octopus 900 perimeter. Our Ophthalmic Genetics Service routinely utilizes both perimeters in clinic.
There are two types of visual field testing—static and kinetic.
Static Visual Field Testing
Static visual field testing systematically plots the field of vision using threshold testing with flashing light presentations of various intensities. This type of testing allows the determination of retinal sensitivity in any given location. It is extremely useful in picking up subtle visual field defects and is a good way to monitor slight changes from year to year. During this test, you will be seated at either the Octopus 101 or 900 perimeter. You will then be asked to look straight ahead at a central fixation target and click a button every time you see a light appear. When the test is complete, a map of the results shows your visual field.
Kinetic Visual Field Testing
Kinetic visual field testing uses moving targets of various light sizes and intensities to map out the entire visual field, as well as the blind spot and any scotomas (decreased areas of vision). This type of testing is useful for mapping visual field sensitivity boundaries. During this test, you will be seated at either the Octopus 101 or 900 perimeter. You will then be asked to look straight ahead at a central fixation target and click a button as soon as you notice a moving target come into your field of vision. When the test is complete, a map of the results shows your visual field.
The ophthalmologist then compares the data (from both static and kinetic visual field tests) with age-correlated normal data and interprets the results.