Visual field testing is performed during a routine eye test to analyse a patient’s visual field.
Visual field testing helps determine the full horizontal and vertical range of what can be seen peripherally by the patient and is used to help diagnose conditions like glaucoma. It is one of a number of common eye tests performed at London Eye Unit.
A visual field test can assess any potential blind spots in either eye. These blind spots (scotoma) could indicate signs of eye disease which, depending on the size and shape of the blind spot, could be linked to optic nerve damage caused by glaucoma.
Brain abnormalities such as those caused by strokes or tumours can also affect the visual field. The visual field test is often used to determine the location of the stroke.
There are two main methods of testing:
Lighted targets are moved from outside of your side vision, towards the centre of your vision until you see can the target. You then indicate to your consultant as soon as you can see the target.
Fixed targets appear more suddenly at random areas of your vision field. You then indicate to your consultant as soon as you can see the target.
Each eye is tested separately and sometimes your Consultant will want to repeat the visual field test right away to make sure the results are accurate.
The tests are repeated at appropriate time intervals to determine if vision loss is progressing or remaining stable. If you are diagnosed with a particular disorder or disease, such as glaucoma, visual field tests become a routine part of your treatment.
Confrontational visual field exam
This test is typically used as a preliminary examination for screening purposes. One eye is covered while the other fixates on a target object in front of you. The Consultant then checks your peripheral vision by asking you to describe what you can see in the far edges of your field of vision, or the Consultant might move their hand in and out of your visual field to determine your range of side vision.
Other tests used for measuring visual field loss include:
Automated perimetry – measures responses to the presence of objects in different areas of your field of view.
Electroretinography – test measuring the electrical activity generated by the photoreceptor cells in the retina.
Frequency doubling perimetry – based on an optical illusion appearing on-screen with vertical bars in contrasting colours at different frequencies, indicating response to light sensitivity in the retina and any optic nerve damage.