7c - Simultanagnostic Vision

Posted by Helen St Clair Tracy in Level 7 - CVIs Movement and Dorsal
Published: 28/01/2020, 12:57am | Updated: 24/02/2020, 7:36am

Video Link: https://vimeo.com/392273519

Before explaining this CVI, let's get all the really big word out of the way!

Simultaneous is a well-known word, meaning things occurring at the same time, doing things at the same time, or things happening together.

Agnosia means not knowing.

Together, these words, in relation to vision, means that a person struggles to see more than one thing at a time.

The definition for simultanagnosia could be explained as:

Simultanagnosia: An inability to see more than a two or three items at once in a scene in which there are lots of items.

CVI Scotland

We use the terms simultanagnostic and simultanagnostic vision to represent our wider understanding of this complex visual impairment affecting looking or searching for things, because the term simultanagnosia has a very specific and limited medical definition.

Visual Search (looking for things)

Simultanagnostic vision is all about difficulty looking for things, or more specifically difficulty finding things.

Professor Josef Zihl

Look at this image (above) and find the diamond. Like most people with typical vision, you could probably spot the diamond immediately, in a fraction of a second, because you were able to process the whole image - to do this, your visual attention is wide enough to see everything.

What if we covered the image with a black blanket leaving only a small hole (above), and told you that behind the blanket were eleven dots and one diamond, and to find the diamond you could only move the hole - how would you find the diamond then? How would finding the diamond be different to the first time?

Looking for the diamond with only a small hole represents the challenges many with simultanagnostic vision face looking for things. But looking for things is not just about finding house keys or the coffee jar in the cupboard. Looking is what we do all the time when we are awake and have our eyes open. So, when looking is impaired, it affects every part of our life.

These dots and the diamond were from a test to find out how people with and without simultanagnostic vision search. Here's how people with typical vision and simultanagnostic vision moved their eyes to find the diamond (below):

Professor Josef Zihl (diagrams)

With simultanagnostic vision, the search looks almost random, and this is what has been repeatedly described to us.

So, to understand the world of the person with simultanagnostic vision, maybe think of how life would be more difficult if someone put a cloak over your head and you only had a small hole to see through...

So, when somewhere busy, like a busy street, there can be very little available information to make sense of where you are. Looking at the image above, you could be standing in a green park, about to bump into something or be in the middle of a road in danger of being hit by a car! Where are you? How are you feeling?

  • Anxious?
  • Confused?
  • Frightened?

Welcome to the world of people with simultanagnostic vision, many of whom reply upon memories to build up a mental map of where they are. So while they are only aware of a small amount visually, in their mind the rest of their environment has been mapped, so they are supplementing their very limited vision with memory maps.

This may be a well-known street, but even with the best memory map, there can still be hazards that aren't part of the mind-map, including:

  • Things to trip over like litter, or signs on the pavement
  • Things that move - people, dogs on leads
  • Things to bump into - cars parked on the pavement
  • People you know but ignore, so offend, because you don't see them

So, life can be pretty treacherous, even in the most known places.

What about somewhere unknown...not miles away, just a wrong turning and you end up on a street you don't know...

  • Where are you?
  • Are you even safe?
  • How are you going to get to where you want to be?
  • How are you feeling at this moment? Extremely vulnerable?

We are not going to give you the whole picture, the person with simultanagnostic vision will never get it, it is their life we are trying to show you.

And for the same person, when somewhere open, with less crowding or clutter, there is less for their brain to map, and vision can be near typical.

So there would appear to be a range of reduced visual attention due to simultanagnostic vision, made worse by complexity and clutter.

The person is not going to be aware of this changing vision. If they have had simultanagnostic vision since birth - it is their normal, and completely understandably, they assume everyone sees as they do - why wouldn't they? And the things they find difficult are given different reasons, like...

  • learning delays
  • reading and writing difficulties
  • clumsiness
  • shyness
  • challenging behaviours
  • obsessive

All these can all have the same underlying cause (limited ability to see a lot at once), but can easily be mistaken as these labels (below)...

And where vision is not considered an issue, the approaches to support might be wrong or limited, or they might actually be adding to difficulties - making things worse! This means that simultanagnostic vision needs to be considered as a possible contributor to all of these conditions.


Visual complexity is not just about how much clutter the brain has to map in terms of detail. Some things are less complex in terms of visual acuity and colours, but more complex to process, particularly...

the human face. We will look more at this in the lessons on recognition, but with simultanagnostic vision, the incredible processing demands when engaging with another person, mean that less is mapped...

who are you?who are you?

...making recognising people by their faces alone extremely challenging, and recognising and interpretation their facial expressions even more challenging.

People with severe and complex needs

What about for very complex children and adults, who may have limited communication, who have been affected by simultanagnostic vision since birth? This may also be their normal, but how might this profoundly affect their learning?

Their visual experiences are not absent, or simply reduced as with ocular visual impairments, they can be:

  • Inconsistent
  • Untrustworthy
  • Frightening
  • Confusing

Making learning anything (see Level 2) extremely compromised, and this is where we believe, many of the profound learning difficulties common with this group, may come from.

Acquired Simultanagnostic Vision

The part of the brain affected to cause simultanagnostic vision (the posterior parietal lobes), is a vulnerable area commonly affected where there is any type of brain injury, including stroke, dementia and multiple sclerosis.


Let's take for example, Emily. Emily had a stroke and is quite nervous about going out. Emily has developed simultanagnostic vision but does not know it, and it has not been diagnosed, because it is not part of routine vision testing.

This is the street (below) where Emily has lived for over ten years, so she knows it very well.

This is all Emily sees of her street when walking now (below)

But Emily is unaware her vision has changed. This seems remarkable doesn't it - how can't she realise her vision is different? But Emily has filled in the missing bits with her visual memories, but is a little more clumsy than she was, putting it down to a lack of concentration, probably something to do with her stroke.

Oh no, Emily has taken a wrong turn, she knows all of these streets, but feels completely lost

Suddenly a car passes, it feels like it is right in front of her face - terrified, Emily starts to frantically look around trying to find a clue of where she is

But she can't put the pictures together - another car flies past, this one honks its horn loudly.

Emily's daughter received a call, her mother was found crying, shaking and disorientated, could she come and pick her up?

Does this mean Emily cannot any longer have any independence and is not safe to be alone? ABSOLUTELY NOT! Emily can be taught strategies to help, Emily has a visual impairment.

Targeted Support


If nothing else, de-clutter. How much by?

We know a teacher who is extremely careful to reduce clutter around her children with CVI - one day a boy she was teaching would not focus on the activity. The room was completely clear, apart from one thing...

A single black electric plug on a wall, that was all it took for this boy to be unable to focus.

For many affected, their memory is a great strength to counteract the visual difficulties, but memories need to be built and added to, a bit like building a jigsaw.

There are techniques that can be learnt, to put together a whole picture a bit at a time, for example by finding a point in the middle, and slowly working out in different directions and returning to the middle (Wagon Wheel approach, see below for more information). This requires the person to be calm, and we know simultanagnostic vision can be extremely stressful, and stress makes the vision even more difficult - a downward spiral! So techniques to stay calm are just as important, for example deep breathing.

Visual Behaviours

As we explained, simultanagnostic vision can manifest as an enormous range of difficulties affecting:

  • All levels and aspects of learning
  • Literacy
  • Social Confidence & Relationships
  • Ability to participate in sports and other activities
  • Behaviours, including developing challenging behaviours
  • And much more!

We commonly come across more able people with simultanagnostic vision who have been identified as having

  • Asperger's Syndrome / Autism
  • ADHD
  • DCD
  • Dyslexia

Here's where it gets complicated...

  • in some, their CVI, particularly their simultanagnostic vision can fully explain the difficulties attributed to something different, for example autism, however...
  • in others, their simultanagnostic vision can only partly explain their difficulties, and there is something else creating barriers to learning, understanding and development in addition to the CVI, and...
  • in others, they still fit the conditions, for example for autism or DCD, but CVI is not present, and their difficulties are wholly attributable to something else.

What is important is to understand firstly if CVI is present, and then which CVIs, and see if they are wholly responsible, or partly, and slowly start to untangle the complicated knot by matching support to known difficulties.

A person with simultanagnostic vision may find it difficult to stay focused on one thing, and may also find themselves fixed on something they can't move away from. For more complex people, bright light sources can be particularly problematic.

Self Referencing

Looking straight ahead, what does what is behind you look like? You don't know because it is not mapped. Whilst this is clearly because 'behind-you' is outside of the range of your eyes, this 'not being there' is how simultanagnostic vision is described, apart from the fact that for everyone else it is there - right in front of them! It can be hard to believe that someone who can read a small text message on their phone is unable to see someone standing right next to them - but this happens, all the time. The person next to them expecting to be visible might as well be standing behind them expecting to be visible!


Before moving on to the next lesson please check you understand the following:

  • The difference between looking and seeing
  • Why we use the term simultanagnostic vision rather than simultanagnosia
  • How simultanagnostic vision affects searching visually for things
  • That simultanagnostic vision can range between being very limited to only somewhat limited
  • What that change in 'range' entails for the affected person
  • Factors that affect the range of simultanagnostic vision
  • Different non-visual difficulties simultanagnostic vision can look like
  • Different approaches to help

Next lesson Level 7d CVIs Movement and Dorsal - Apraxia of Gaze

Further reading is not necessary to proceed, but if interested you may find the following enjoyable:

Simultanagnostic vision entails a wide range of difficulties and experiences, and we have written a great deal about it on this website. As a broader introduction, we recommend you read our pages under the Simultanagnosia Spectrum.

3Z (Zoom-In Zip-Up Zoom-Out) explains our suggested approach of building up experiences with memories a bit at a time, to understand a more complicated or bigger environment or experience.

Wagon Wheel Approach - an approach to try to build up a bigger picture when needed.


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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.