To test your peripheral (side) vision, your your optometrist may perform a Visual Fields Test during your appointment at Sharpe Optometry in London.
Why do I need a Visual Fields Test?
A Visual Fields test is often performed as part of an eye exam, in order to determine the full vertical and horizontal range of your peripheral (side) vision, and how well you can see objects in your peripheral vision.
Visual Fields Tests are done to asses whether or not there are any blind spots in your field of vision, as these blind spots can sometimes indicate the presence of certain eye diseases.
For example, glaucoma damages the optic nerve, which leads to a very specific visual field defect.
Brain abnormalities (for instance, those caused by strokes) can also create blind spots. As a matter of fact, it's possible to detect the location of a stroke or a tumor in the brain based on the shape, size, and location of a visual field defect.
What types of Visual Fields Tests are there?
Confrontation Visual Fields Test
This type of test is usually performed as a screening test. One of your eyes will be covered, and you'll be asked to fixate the other on a target object (often the optometrist's open eye). You'll then be asked to describe what you can see on the far edges of your field of view.
Automated Perimetry Tests
These tests measure a subject's responses to various objects in the periphery of his or her vision.
During this test, you'll be asked to stare straight ahead at a light, holding your head very still. Then, random lights will be flashed in various positions and intensities in the periphery of your vision.
Each time you perceive one of these lights, you'll indicate your response with a button, or some other signal you and your optometrist have agreed upon.
If you can't see certain lights, it may indicate the presence of a blind spot, or vision loss.
Frequency Doubling Perimetry Test
Frequency Doubling tests use an optical illusion that is produced using vertical bars of contrasting colours (typically black and white) that appear on a screen. When these bars alternately flicker at high frequencies, they appear to double in number.
If you can't see the vertical bars at certain frequencies, it may mean that you have optic nerve damage, or other types of eye damage, with accompanying vision loss.
To measure the electrical activity of photoreceptor cells in the retina, this test stimulates the eye using a special strobe light, or a reverse checkerboard light pattern.
This type of testing is typically done to diagnose certain hereditary or acquired disorders of the retina, such as a deteched retina, retinitis pigmentosa, or the functional changes to the retina that can be caused diabetes or arteriosclerosis.