We are in a supermarket, and have spotted the lady with grey hair - using a simple oval shape to very broadly illustrate a full visual field:
Image 1: This is a photograph - nobody sees like this.
None of us have perfect clarity across our entire visual field - whatever we are looking at has most clarity, and this is reduced proportionately the further out of the point of focus, towards our periphery vision we go, so...
Image 2: This may be closer to typical vision, what we are looking at (the grey haired lady) we see clearly.
Here, there is sufficient clarity in the periphery vision to do things like spot the flowers on the left or be aware of a sudden movement, like someone coming out of the aisle, and because we have sufficient vision to see them, we can redirect our visual attention, so the point of highest clarity moves from the old lady to the flowers ahead of us - we can do all this because we do not have simultanagnosia.
Image 3: Mild simultanagnostic vision.
Simultanagnostic vision varies from person to person - here (above) there is much less clarity outside of the central point - this might be the case for someone mildly affected, who probably relies upon memory to find things, because visual search is often difficult, especially as things become more crowded and busy.
Image 4: More severe simultanagnostic vision
This could be a different person more severely affected, or the person above (Image 3), as things are getting more challenging, maybe there is an announcement over the speaker or they are simply getting frustrated and stressed. In this case, they are unaware their vision is getting worse, but now they will have no idea if someone walks out of the aisle on the left, until they bump into them.
Image 5: Very severe simultanagnostic vision
And this is remarkable, because we know from many first hand accounts that often people aren't actually aware when what they see has altered, often due to environments being too challenging, and they can hardly see at all.
This is why simultanagnosia is such a nuisance - you often don't know you can't see!!!
Simulation of simultanagnosia is difficult, because we are trying to simulate something that is often not conscious, so how can we know what it is actually like?
We can't, for certain, but we have worked together with adults who have come to gain awareness of their simultanagnosia, so as to obtain the closest simulation that we can for the present.
The blurring in the periphery of the images is meant to represent degrees of reduced visual attention for anything not being directly looked at, and should not be confused with reduced visual acuity.
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