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Lessons

3d - Visual Fields

Posted by Helen St Clair Tracy in Level 3 - Introduction to the Visual Brain
Published: 07/03/2019, 12:03am | Updated: 15/03/2019, 6:09am

Video Link: https://vimeo.com/323459644

Your visual field is the area that you can see, a bit like a physical field, it is a measure of space.

The outer edges of your vision are called your peripheral vision

The outer edges of your visual field, illustrated here with red crosses, are called your peripheral vision.

Your visual field is made up of vision from both your left and right eye.

There is a large overlap in the middle.

Look straight ahead and make a note of what you can see furthest to your right. Now cover or close your right eye, and make a note of what you can see furthest to your right. Your right peripheral vision has been slightly reduced, but you have not lost the ability to see everything on your right side because you have closed your right eye, as there is a cross over with your left eye.

Looking at the image below, the picture of the house and trees is seen by both eyes.

For the visual images to be processed, they are turned round, both vertically and horizontally.

The visual information travels to the primary visual cortex in the occipital lobes (see lesson 3b) along the visual pathways between the eyes and the brain...

The visual information travels to the occipital lobes in the form of optic radiation.

From the eyes, the visual information travels through the optic nerves, the crossover at the optic chiasm, along the optic tracts to the optic radiations.

Optic Radiation & Lower Visual Field Impairments

The upper part of the optic radiations on both sides serves the lower part of the visual field. They sweep through the posterior parietal lobes, over the top of the water spaces on both sides, the lateral ventricles. A lower visual field impairment affecting both eyes is often due to these optic radiations being affected in both posterior parietal lobes.

Visual Field Impairments

There are many different types of visual field impairments, including:

  • Lower Visual Field Impairments - typically caused by a problem with the optic radiations (although can be caused by occipital lobe damage)
  • Hemianopia - different types, caused, for example by occipital lobe damage

Some people may have a number of visual field impairments.

Checklist

Before you move onto the next lesson, please check:

  • You understand what your visual field is
  • You understand that your visual field is created from information from both of your eyes, which has a large central overlap
  • You understand that the brain flips the image of what you are looking at both vertically and horizontally to process it
  • You know the visual information reaches the occipital lobes on optic radiation
  • You understand that visual field impairments can be caused by different parts of the brain.

Next lesson: Level 3e An Introduction to the Visual Brain - Movement

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At CVI Scotland we are devoted to helping people understand cerebral visual impairments, and together working towards developing the understanding of this complex condition.