Types of Visual Field Tests
A confrontation visual field exam is performed with the doctor ‘confronting’ you by either standing or sitting directly facing you. One eye is focused on a set point and the other is completely covered. Your doctor will then ask you to specify what you see in your peripheral view, or off to one side.
A common way of assessing your peripheral field of view is for the tester to hold up a set number of fingers, and ask how many are visible to you while still focused on the object.
Additional exams will be needed if any abnormalities are detected. More comprehensive diagnostic tests are available to get a more in-depth analysis. Here is a list of sensitive tools used to measure the quality of your vision:
Automated Perimetry Tests
- There are a number of tests used to measure your ability to perceive objects in various areas within your visual field. Automated perimetry tests involve staring ahead at a light source, while randomly placed, mini flashes of varying intensities are activated. Each time a flash is visible you will instantly acknowledge it by pressing a button.
Vision loss is apparent if you can’t see the flashing lights at any point in the test. You may have blind spots.
Frequency Doubling Perimetry Tests
- The optical illusion of upward bars, usually alternating black and white, visual on a screen, is known as frequency doubling. Vision problems that hinder the ability to see these bars at specific frequencies may be the result of optic nerve damage or some other disorder.
- Doctors use electroretinography to measure the electrical activity produced by the retinal photoreceptor cells when the eye is stimulated by a targeted light. An electrode is positioned on the cornea to capture the measurement that is recorded by an electroretinogram or ERG. An ERG is a powerful device used to detect and diagnose a number of eye diseases and other disorders.