Visual Field Testing
A visual field test measures an individual's entire scope of vision, that is their central and peripheral (side) vision.
It maps the visual fields of each eye separately. It is a subjective examination, requiring the patient to understand the testing instructions, fully co-operate, and complete the entire test in order to provide useful information. Because it requires a high degree of concentration by the patient we normally schedule a separate examination time to perform these tests.
Visual field testing is most frequently used to detect any signs of glaucomatous damage to the optic nerve. In addition, it is useful for detecting central or peripheral retinal disease, optic nerve disease, and diseases affecting the visual pathways within the brain.
Virtually all visual field testing is performed one eye at a time, with the opposite (contralateral) eye completely covered to avoid errors. The patient must look straight ahead at a fixed target, in order to avoid incorrectly testing the central vision rather than the periphery.
Most modern computerised visual field testing devices also continuously monitor fixation or the ability of the patient to maintain a consistent straight ahead gaze.
What exactly is your visual field?
If you covered or closed your left eye and held a pen at arm’s length, straight out in front of your right eye, and stared at the tip of the pen, you would still be able to see things out of the corner of your eye and objects approx 60 degrees to the left. You would also be able to see objects to the right of centre, almost right around through 110 degrees, and approximately 60 degrees upwards and 70-75 downwards. The opposite would apply if you covered up or closed your left eye. This is your monocular visual field. With both eyes open you would be able to see 200 degrees laterally and 130 degrees vertically. This is your binocular visual field.
Eyecatchers Optometrists Invercargill Practice: 22 Kelvin Street – Ph: 03 218 8561 Gore Practice: 108 Main Street – Ph: 03 208 9244
