Visual attention can vary, sometimes considerably, degrading what the person can see, and can be due to a lot of factors, which may include:
Note how many are duplications from the previous list of 'how optic ataxia can make you feel'.
How optic ataxia makes you feel has a direct effect on your vision.
Let us return to the big red chair.
The person is aiming to get the milk, which entails a journey through space. This is challenging for them, and requires great concentration. They will walk into the red chair, every time, for the person it simply isn't there - they can't perceive it because they are concentrating on getting the bottle
The person can't accurately judge the distance to the bottle, and may have their hand out ready to grasp much sooner than needed, or knock it over when they get to it.
As soon as they get the bottle their visual world will change as the focus moves elsewhere.
Having tripped over the red chair they may well now see it and choose to lie on it to drink their milk. Within a few seconds the enormous chair has been not visible (unperceivable) to the person, then has become visible (perceivable).
Furthermore, changing the meaningful bottle of milk, to meaningless blue glasses, completely alters the person's visual world. What the person sees is completely unique to them and their likes and dislikes, based on their life's knowledge and experiences.
This example demonstrates simultanagnosia, optic ataxia and lack of visual attention all working together:
Simultanagnosia meant that the person could see the bottle but not the chair (in the middle picture), because the bottle was the interesting / meaningful thing the person had found. Where there wasn't anything with a very strong draw for the person (as in the bottom picture with the blue glasses) they are able to have a general visual view, possibly the closest they will come to regular vision. They are not drawn to the blue cups because they have no meaning, but the person would have seen them and awarded them no interest thus no visual attention.
Optic ataxia presented challenges in physically getting to the bottle, which required a lot of concentration, and a bit of anxiety (risk of falling, tripping) creating lack of visual attention.
Lack of visual attention - demonstrated by the decreased visual awareness of the red chair which was bumped into (middle picture). With the blue cups, there was never any desire to retrieve them, so the hurdles created by optic ataxia are not relevant here, so the person remained relatively calm thus the image was hardly affected by their simultanagnosia or reduced visual attention.
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