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Optic Ataxia

Optic Ataxia (Problems Judging Distance and Depth to guide movement)

Optic ataxia is difficult to demonstrate with pictures because it is all about difficulty reaching and moving through three dimensions. We talked about simultanagnosia, and how our brains create a seamless image of our surroundings. Our brain simultaneously gives that image depth, and is responsible for all the micro calculations we subconsciously perform to move safely through any given space. We guide our movements in this way without being consciously aware of doing so. Optic ataxia is where this perception of depth, to guide our movement, is altered or degraded, and is best explained with examples:

Example 1. Picking up a cup with Optic Ataxia

Go back to your cups and reach for one of them. Your hand will be guided through space to meet the cup at the point where it is situated, and bring it back through space to your mouth, and tilt it through space to drink. Your brain has just effectively performed multiple calculations including distance, depth and weight (enough strength to lift the cup but not so much that you lift it too fast and spill the contents).

Let's go through the same activity but with optic ataxia.

1) Firstly, you won't have a very good sense of depth. If the cup is on a nice clear surface it should be easy to locate, but if it is on a cluttered desk it will be harder to find, because its depth (three dimensions) may not stand out - it's just another flat thing on the desk like papers, pens, staplers etc.

2) Reaching for the cup through space is difficult - you don't know where it is, so a safer route is to run your hand along the table surface to aid guidance using touch as well as vision.

3) You can see the cup, and that your hand is at some point going to make contact with it, but you aren't quite sure when. Sometimes it's sooner than you expect and you knock it over. Sometimes it's further than you think and you end up grasping at thin air.

4) Everyone, including you, think you're really clumsy!

Example 2: Picking up another cup with optic ataxia

Place an empty cup on the left hand end of a table and sit straight in front of it.

2) Place a row of coins on the table to the right in 6 inch intervals.

3) Look at the cup, then look at the first coin. Whilst looking at the coin, attempt to pick up the cup.

4) Repeat with the next coin, looking at the coin only, try to pick up the cup.

5) Continue repeating along the line of coins, just looking at the coin whilst trying to pick up the cup.

You are becoming more optically ataxic. The cup is in your peripheral vision, where the voxels (which are like three dimensional pixels) are bigger. As the voxels get bigger, acuity (clarity of vision) is reduced, and the task of picking up the cup becomes more challenging, but remarkably, if you get someone to video you, you will see that you automatically adapt.

  • First the gap between your fingers and thumb gets wider as the cup is more to the side.
  • Next you place your hand down on top of the cup to locate it better through touch,
  • Then next you may automatically choose to gather it up (scooping it from behind).
  • You also get slower and more hesitant, having to make mid-course corrections with reaching hand when reaching far to the side without looking.

These are very similar to the features of reaching with optic ataxia.

Example 3. A Trip to the supermarket with Optic Ataxia

This scenario is applicable to an adult or child walking, or being pushed in a chair or shopping trolley.

Imagine you are in a busy supermarket, looking for fresh vegetables

As you move through the aisle people are moving past you in different directions and reaching across you to pick things from shelves. You can't measure the distance between yourself and the people who are moving. For you the easiest situation is

  • where nothing moves
  • second easiest is where one thing is still and another moves, maybe you walking past the apple stand.
  • Harder still is two people in motion, especially going in different directions.
  • Several people going in different directions is extremely difficult to calculate.
  • Several people going in different directions where personal space is often violated (walking too close, reaching across) can be too much and cause a complete meltdown - why?

this is really important

WARNING!!! When you can't measure distance effectively, as with optic ataxia, you quickly perceive a threat of collision, which in turn will trigger an automatic reflex that we sometimes call 'fight or flight'. A message will be sent to your brain that you are at risk of harm and it will over ride most of your conscious functions and release adrenaline. Once you have reached this stage you will have three options:

1)Get out of there as fast as you can

2)Have a complete meltdown on the spot, which may well involve aggressive physical behaviours

3)Become completely withdrawn.

We call this a CVI Meltdown.

There are techniques to help which we will discuss in the support section, but people with optic ataxia will find the following places stressful, because they can be frightening to them:

  • Shopping centres / malls
  • Supermarkets
  • Airports
  • Concerts / festivals / funfairs
  • Queues
  • Busy corridors (e.g. between classes at school)

Continuing through the vegetables in the supermarket, thankfully it is a quiet morning and there are not too many people around to make you feel too threatened. You see the apples and reach for one, but miss causing the delicately balanced display to tumble to the floor - people start to look and stare. You know the supermarket, but it's not as familiar as home, and as you move on you misjudge the aisles and bump into a pillar with your shoulder. Again, someone notices and looks. Two people are walking towards you, you can feel the anxiety build and stop dead, knowing they are less likely to hit (walk into) you if you are standing still. More stares. People are looking at you like you are strange in some way.

This example leads to another important factor of optic ataxia - how it makes you feel.

How Optic Ataxia can make you feel:

  • Clumsy
  • Conspicuous
  • Embarrassed
  • Useless
  • Frustrated
  • Angry
  • Confused
  • Depressed
  • PhysicallyThreatened
  • Vulnerable

Optic ataxia will affect everything you do. Many people with optic ataxia don't know or understand that they have it, they just think they're a bit clumsy and rubbish (as with simultanagnosia). They're not, these tiny calculations only need to be slightly out to create havoc, as with the supermarket example above.

Without understanding, behaviours will develop. The person may avoid embarrassing situations, and choose an increasingly isolated life. These behaviours could be labelled as autistic

Those without communication skills will demonstrate their anxiety by screaming, crying or wailing - obvious signs of discomfort to those who know them well

These behaviours are founded upon FEAR, and a very real physiological response to fear. The behaviours have to be treated with enormous respect and managed extremely carefully.

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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.