What is a visual field test?

Visual field testing is a common eye examination often performed during a routine check to analyse patient’s visual field.

The visual field test measures how much ‘side vision’ you have and it’s used to help diagnose conditions like glaucoma.

 

 

 

 

It helps determine the full horizontal and vertical range of what you are able to see peripherally. Essentially the test measures how much ‘side vision’ you have and it’s used to help diagnose conditions like glaucoma.

At London Vision Clinic, we have the relevant equipment for testing your visual field and can perform these tests in-house.

Please contact us to learn more about visual field testing.

The purpose of a visual field test

The purpose of a visual field test is to assess the potential presence of blind spots, which could indicate signs of a variety of eye diseases. Depending on the size and shape of the blind spot (scotoma), it 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.

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Types of visual field tests

There are several ways in which this examination can be performed.

Essentially there are two main types of testing methods:

Moving targets

This test involves lighted targets being moved from outside of your side vision and in towards the centre of your vision until you see the target. As soon as the target appears, you would indicate this to the doctor – usually by pressing on an indicator button.

Fixed targets

This test involves fixed targets, these appear more suddenly into different areas of your vision field (onto a screen). As the target appears, you would indicate this to the doctor, again usually done by pressing a button.

Please contact us to learn more about visual field testing.

How the tests are performed:

Confrontational visual field exam

This test is typically used as a preliminary examination, used for screening purposes. In its simplest form, one eye is covered while the other fixates on a target object (eg, doctors open eye) and then you are asked to describe what you see in the far edges of your field of view, or the doctor moves their hand in and out of your visual field to determine the range of side vision.

Other more comprehensive formal types of visual field tests are used for measuring the visual field loss include:

  • Automated perimetry – measures responses to the presence of objects in different areas of your field of view.
  • Frequency doubling perimetry – based on an optical illusion appearing on-screen with vertical bars in contrasting colours at different frequences, indicating response to light sensitivity in the retina and any optic nerve damage.
  • Electroretinography – test measuring the electrical activity generated by the photoreceptor cells in the retina

 

Each eye is tested separately. Sometimes the doctor will want to repeat the visual field test right away to make sure the results are accurate. If the patient is tired, for example, the test results can be unreliable.

Visual field testing is used to measure peripheral vision loss. 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 galucoma, visual field tests become a routine part of your treatment.