Simultanagnosia - The brain is confused by a busy visual scene
If you have come across children, whose eyes are tested ‘normal’, yet still have problems making sense of what they see, you might be dealing with a CVI called ‘simultanagnosia’. This is not common but can be profoundly disabling. It prevents a person seeing and comprehending many things at once, yet they can see single objects if presented on their own against a contrasting background. The world can become a chaotic, confusing place, and the child may be over-stimulated and overwhelmed. Those with severe simultanagnosia have a limited window of visual attention and cannot see more than one object at a time. It’s a little like tunnel vision. Their world is patchy and disjointed; it’s sometimes called the ‘Swiss cheese effect’. So they pick out an object, but they miss the "big picture."
I have come across this a few times. A little boy with microcephaly, (a condition where the brain is under-developed), demonstrated it dramatically one day. He was sitting on the floor with three toys in front of him. Initially he looked blank, not knowing what to pick up. One toy was removed and he still looked blank. Then another was removed, leaving one and immediately he appeared to recognise the last toy and picked it up. I think this shows that to this boy the world was cluttered and confusing and he needed it greatly simplifying. Once the number of objects in the scene in front of him were reduced he was able to make sense of it; he recognised a favourite toy. The young man later went to a special school for children with severe learning difficulties, where in my view there was a lot of visual clutter, and noise. I suspect that this did not help his learning. A common issue in special schools (see article on Minimalism).