What is CVI?


Simultanagnosia Spectrum

Simultanagnosia (difficulties seeing the whole image at once)

If you look up the word simultanagnosia you'll see that it refers to being able to only see a single part of a visual scene at a time. This description is found in research papers describing the condition in adults.

As parents and those affected we see a more menacing disability. One that impacts profoundly upon all aspects of our everyday lives. We have therefore chosen to give the word a wider meaning. One that more truly reflects our day to day experiences of living with a type of vision that is limiting, variable, fatiguable, affected by stress, difficult to explain and frustrating

The visual difficulties we describe below are seldom recognised professionally, because affected children cannot describe their vision, and we understand that a test to truly identify their nature and cause, particularly in children, has yet to be invented. Nevertheless we are describing our experiences and understanding, because it is clear from our combined observations and contacts, they are very common.

To understand simultanagnosia, try putting two cups in front of you, a few centimetres apart. Look at the one on the left, and without moving your gaze, consider what you can understand about the cup on the right. You may remember that it has writing on it, and what it says, but you can't read it. You can probably recognise that it's a cup still.

As you are concentrating on this little activity, your awareness of the rest of your visual field has degraded further, as demonstrated below showing how the background loses clarity.

Simultanagnosia is sometimes explained as an inability to see more than one thing at a time, or an inability to see many things at once. Actually, none of us can clearly see more than one part of the picture at a time, as our little experiment demonstrates. Our brains are brilliantly able to create seamless three dimensional images from the information they get through our eyes, as they dart about picking up each part of the scene, enabling us to see what we are presented with as a whole image.

Simultanagnosia is not so much an inability to see more than one thing at a time, it is a difficulty in putting together and seeing the whole image simultaneously.

Connor has simultanagnosia and loves red things. Connor is drawn to the red balloons in this picture, particularly the red balloon on the right.

Connor might be able to find the other red balloon, but he couldn't see the green or white balloon

When presented with a bunch of all red balloons...

...Connor may see the whole bunch, like this.

Looking at the image of the red chair below, we would think that Connor, who loves red, would see the chair quite clearly.

Connor however doesn't see the chair at all, in fact he bumps into it. This is because Connor has spotted something more interesting, in this case a cup of milk. With a bunch of coloured balloons, the red one wins, with a red chair and cup of milk, the milk wins

Simultanagnosia is not about size or colour or contrast, it's about what is important and interesting to that individual person, at that moment in time.

Simultanagnosia explains how a person can see something reasonably small, but at the same time miss something enormous (demonstrated by bumping into it).

Here's the image with people and red balloons again.

Mary, who has simultanagnosia is looking at it and only sees the interesting face of the old man, not the balloons, which have the highest level of contrast in the picture.

Simultanagnosia is completely personal to the individual.

Connor's mother tries to explain the challenges of simultanagnosia:

"I was once invited to observe whilst Connor was bring assessed. I sat opposite him, across a narrow table, maybe 50cm wide. The VI teacher was very pleased to show how he could pick up a shiny sweet from the table. I pointed out that he couldn't see me, his mother, from a similar distance. At another assessment Connor looked at something even smaller, the size of a shirt button. I asked how it was that he could see something so small, yet the same morning walk into a closed door and fall over an armchair that had been in the same spot for years. It was so frustrating, we didn't understand Connor's vision at all. The people who supported us were lovely, and tried to be helpful, but none of them explained Connor's visual world to us - how he could see a small button or sweet, but not see me or a large armchair. One professional told us it was because he wasn't 'looking' but didn't give us any further explanation. I feel as though we lost years of important learning and developmental opportunities, because we didn't understand Connor's visual world."
Why could Connor see the shiny sweet and not see his mother, from a similar distance, in the same room at the same time?Connor has poor clarity of vision, low contrast sensitivity and simultanagnosia. Any one of those would make identifying people using visual facial recognition challenging. With all three, and at a severe level as they are with Connor who is registered blind, it is clear that he is unable to recognise people by their faces and needs other information. Connor's mother confirms that even at home, if someone else is in the house he is likely to go up to them thinking they are his mother, and it isn't until he holds and smells their hands that he realises his mistake. During the assessment Connor's mother was in a place he didn't expect her to be, she sat quietly so he could not use her voice to identify her, and in the circumstances wasn't interesting enough to draw his attention, unlike the shiny sweet in front of him.
It wasn't that he couldn't see her, it's that he didn't see her. He didn't see her both due to not being able to recognise faces and having simultanagnosia. The shiny sweet took his visual attention.

Notes: Connor was in a test room with people he was unfamiliar with (although a known teaching assistant was nearby). Connor didn't appear frightened, but would have been confused, which would not create the optimal testing environment. We know that Connor needs high levels of contrast, and a width thickness of at least 0.25cm for something to be visible. The shiny sweet was the single object on an uncluttered white table in a quiet empty testing room and would not have been difficult for Connor to see, but what does that tell us about Connor's visual world? Very little. In Connor's classroom, where every wall and surface was covered in clutter, and the space was shared by many other children and professionals, it is unlikely he would have seen the shiny sweet even if it twenty times the size. Connor's poor clarity of vision and low contrast sensitivity create significant challenges understanding his visual environment, but they are not as great as the challenges created by his simultanagnosia. Connor's visual world changes, sometimes from one second to the next, from safe to terrifying, sometimes for no obvious reason, due to his simultanagnosia.

Looking & Seeing

You may have been told at some point that you can only see something if you look at it. Mary, who only saw the old man in the above picture didn't 'not see' everything else. Mary's brain processed the image and drew her to what was interesting to her. Mary was then unable to move away from the old man's face, and thus unable to make up the whole picture. Mary chose the man based on her preference, which is cemented in her life's experiences and preferences.

This is why CVI is so deeply deeply individual and personal. Generic systematic approaches will never work because a detailed personal knowledge of the individual is required to make sense of how they see and how to adapt to meet their needs.

For people with simultanagnosia, when a place is familiar, for example home, and there is a routine, it is much easier to manage and find things visually. If the bottle of milk is always left on the table by the red chair the person will go looking for it and should easily find it. The further you move away from familiarity and routine, the more challenging tasks become.

People with simultanagnosia often demonstrate a strong preference for routine for this reason, which can be misinterpreted as a sign of autism.

A child may easily find and go to their mother at home, but not see her sitting in front of them in a different setting, maybe at school. The person will use their memory of where they are and what is normal. When they are somewhere new, they have no memory to assist them, and feel vulnerable. Most people are unaware that they have simultanagnosia, they believe this is how everyone sees the world.

The first time Mary truly understood the extent of her simultanagnosia was when it was being demonstrated to a large audience. Mary was sitting at the front of the room and was asked to glance up at the audience and say how many people she saw. To her surprise, only one face was clear, the rest of the scene around this person was simply not there - it wasn't black, just didn't exist. She then looked down, before glancing back up again. This time she saw another face, but not the face that she had seen the first time and she had no idea where this new face was in relation to the first face she saw. By this stage, Mary was feeling very anxious, as she knew that there were lots of people in the room, but she just couldn't find them. Every time she glanced away from the audience or switched her gaze around the room, only one face would come into focus and she couldn't work out exactly how many people she was sitting in front of. She also knew that she had a friend in the audience and thought she knew exactly where he was sitting, as she had been sitting with him just moments before. But when she tried to find him, her glances became panicked and she was not able to direct her gaze to where she wanted it to go. Her gaze kept getting drawn to faces that for some reason her brain found interesting, even though she wasn't sure why she was being drawn to look at them. The more panicked she became, the less she was able to focus on until she got to the point where it was easier not to look at the scene at all and just averted her eyes. She also found it stressful when someone from the audience asked her question. Although she could clearly hear the man's voice, she had no idea where he was in the room and wasn't able to direct her answer to him. From this experience, Mary started to understand why, for the first time since her brain injury 17 years earlier, she found crowded situations so hard.

Memory is used as a sixth sense to help cope with simultanagnosia.

The descriptions provided by parents show that simultanagnosia can affect people very differently. It also can present very differently for the same person depending on the circumstances, which may include:

  • if they are tired, stress, anxious or frightened
  • if the environment if busy, noisy, cluttered or crowded

For this reason, we have used the term simultanagnosia spectrum, to allow for these reported wide ranges.


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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.