visual field definition (Split from #61 2.4.4 language)

[allanj-uaag]

#61

from https://lists.w3.org/Archives/Public/public-low-vision-comments/2016AprJun/0003.html

Section 2.4.4
· Poor definition of Visual field. Suggestion: “The visual field is a map of the extent of visual space seen without moving the eye” (Cassin p.219)
· Should be 130 degrees vertical not 150 degrees.

[shawna-slh]

Help Wanted: Will someone research visual field degrees and add the best resources to https://www.w3.org/WAI/GL/low-vision-a11y-tf/wiki/References#Field_of_Vision
(and if there is other info, it goes here: https://www.w3.org/WAI/GL/low-vision-a11y-tf/wiki/Research)

[allanj-uaag]

http://www.perkinselearning.org/videos/webcast/visual-fields
160 deg in each eye horizontally
135 deg in each eye vertically
mileage may vary due to facial type.

On Thu, Jun 2, 2016 at 9:54 AM, shawn_slh [email protected] wrote:

Help Wanted: Will someone research visual field degrees and add the best
resources to
https://www.w3.org/WAI/GL/low-vision-a11y-tf/wiki/References#Field_of_Vision
(and if there is other info, it goes here:
https://www.w3.org/WAI/GL/low-vision-a11y-tf/wiki/Research)

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[shawna-slh]

Rethinking this: The goal for this document is for readers to get a basic understanding of low vision user experiences. I think the degrees doesn't help that. I propose that we focus instead on understanding what it's like.

Previous draft:

Field of Vision
The area from which a person’s eye is able to gather visual information when looking straight ahead is referred to as the field of vision or visual field. People generally have a field of vision of approximately 180 degrees from left to right and 150 degrees up and down, with the sharpest vision in the central 5 degrees and color vision in the central 20 degrees. Some people have a smaller field of vision, which is called field loss.
[bullets, then example images]

Proposal for replacing that paragraph:

Field of Vision
Field of vision, or visual field, is the entire area that can be seen when the eye is directed forward, including what is seen with peripheral vision. Some eye and neurological conditions cause field loss, where people have a smaller or obscured field of vision. For example, significant peripheral field loss, sometimes called "tunnel vision", is somewhat like looking through a drinking straw.
[bullets, then example images]