Our visual field is the full picture of what we see, and is most easily demonstrated as a wide oval (although for a more detailed representation look at images of 'binocular vision' on Google Images).
From a picture, this is our visual field:
Or rather, this is how we think we see it...
Peripheral vision is the part of the image at the edge of the picture we can see.
Looking at the spire in the middle of the picture (below, with the red arrow), what detail can you make out on the far right side
But actually, this isn't what we see either...
Looking again at the spire only, and without moving your focus from the tip of the spire, try to count the columns on the monument to the left of the picture.
Our peripheral vision is not clear.
The above pictures show a little about how we see in our visual field, but not all visual fields are the same. With some cerebral visual impairments part of the visual field is absent, for example with a hemianopia, which will be explained below.
Mary has a right hemianopia, this is how Mary describes her vision to us:
With Mary both the eyes work completely normally, so even though she only sees the left side of the image, it appears to her in the middle of her visual field, and she is not consciously aware that the right side is missing.
Where part of the visual field is missing, as with Mary, it is possible for some to retain a different kind of sight called blindsight. This is where the brain creates a part awareness of movement. This will be explained in much more detail in the following sections.
We have created a new sub-section for Lower Visual Field Impairments, please either click here, or click next, below.
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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.