University of Edinburgh
 

Medical Information on Ocular Motor Apraxia

by Dr Andrew Blaikie for VI Scotland

This document is written with the minimum use of medical terms and jargon. It is impossible to avoid all medical terms but where we have used them we have attempted to explain them as clearly as we can. Although the information is intended to describe most aspects of the condition each child is different and there will always be exceptions to the rule. As far as we can determine these pages are true and accurate and have been written in good faith.

What this information is not for?

This document is not a substitute for a consultation with a Health Professional and should not be used as a means of diagnosing a condition.

We hope the information will help you to:

  • Have a better understanding of the condition
  • Know what tests and treatments are normally available
  • Know when to seek professional advice
  • Be able to discuss the condition in a more informed way
  • Make the most of consultations with carers, teachers and health professionals
  • Be reassured and more able to cope

Due to staffing limitations we are not able to offer telephone or email advice to parents of children.

Medical Information on Ocular Motor Apraxia

What we see is made in the brain from signals given to it by the eyes. What we see is in fact made in the brain. The brain makes sight from signals given to it by the eyes.

What is the normal structure of the eye?

The eye is made of three parts.

  • A light focussing bit at the front (cornea and lens).
  • A light sensitive film at the back of the eye (retina).
  • A large collection of communication wires to the brain (optic nerve).

A curved window called the cornea first focuses the light. The light then passes through a hole called the pupil. A circle of muscle called the iris surrounds the pupil. The iris is the coloured part of the eye. The light is then focused onto the back of the eye by a lens. Tiny light sensitive patches (photoreceptors) cover the back of the eye. These photoreceptors collect information about the visual world. The covering of photoreceptors at the back of the eye forms a thin film known as the retina. Each photoreceptor sends its signals down very fine wires to the brain. The wires joining each eye to the brain are called the optic nerves. The information then travels to many different special 'vision' parts of the brain. Some of these special vision parts of the brain also control the way the eyes move. All parts of the brain and eye need to be present and working for us to see normally.

What is Ocular Motor Apraxia?

'Fast' eye movements are called saccades. We use saccade eye movements to quickly change the direction that our eyes are looking. This helps us look at something that has suddenly moved near to us. This is so the eyes can focus sharply on an object. The eyes can then give clear signals to the brain to make clear vision. It also helps us quickly move our eyes across a page of writing while reading. Saccades are important in many other visual tasks. Ocular Motor Apraxia is a condition where a child has a breakdown (failure) in starting (initiating) fast eye movements.

Ocular Motor Apraxia has many different names. It is sometimes called Cogan's Ocular Motor Apraxia or Saccadic Initiation Failure (SIF). SIF is a useful name to help explain what the condition mainly is: a breakdown (failure) in starting (initiating) fast eye movements (saccades).

What is the cause of Ocular Motor Apraxia?

Many different parts of the brain control eye movements. If any part becomes damaged then ocular motor apraxia may develop.

A child may be born with these special eye movement control bits not working (congenital). Other children may develop it in childhood (acquired). There are many different reasons why a child might develop Ocular Motor Apraxia in childhood.

It is often not the only condition that the child may have. Children may also have:

  • Learning difficulties
  • Delayed language development
  • Delayed sitting and walking skills
  • Delay in toilet training

Very often no cause can be found. Doctors call this idiopathic.

A head scan can sometimes shows a certain part of the brain to be smaller than usual. This bit of the brain is called the vermis of the cerebellum. This part helps the eyes make exact and quick movements. It is not known why some children might have a small vermis.

How is Ocular Motor Apraxia diagnosed and how does it affect the way a child sees?

Ocular Motor Apraxia is often diagnosed by doctors asking parents questions about their child. Children often 'thrust' their head from side to side to change the direction they are looking. 'Head Thrusts' are a typical movement that helps a child overcome their difficulty in moving their eyes quickly. Children may also blink to start a fast eye movement. Parents will notice this. These children often tend to have difficulty reading. They may also dislike travelling in cars, as they will have difficulty seeing things passing by outside of the car.

During an examination of the child's eye movements an eye doctor can confirm the diagnosis. Sometimes other tests are also done. This may be to see if there is a cause for the condition. Often no cause is found. This is called idiopathic.

Does ocular motor apraxia get better?

The lack of eye movement in ocular motor apraxia is first seen during the first few weeks of life. The movements of the head develop later. During this early stage the baby may wrongly be thought to have poor vision because moving targets can't be followed by the eyes. Quick side to side head movements called head thrusts may then develop. Long term follow up has shown that these head movements decrease gradually over a number of years in many children. In addition eye movements can improve with time in some but not all children. It is not possible to predict which children will show improvement and which will not.

How can parents, family, friends and teachers make a difference?

Ocular motor apraxia may develop on its own. It is however more commonly seen along with other conditions. These conditions might cause slowing of some aspects of development. As far as vision is concerned there are a number of things to think about.

We use our vision to get around, learn new things and to meet other people and make friends. Most children with Ocular Motor Apraxia have few problems getting around. The way they act can give the impression that their vision is normal. It is important however to be aware of their own special problems with vision.

It can be difficult for the child to choose to look in a particular direction. This means that the child may not look at you. This does not mean that the child is not paying attention.

The child may find it difficult to follow moving objects, especially when they are small. Television programmes with fast movement, such as cartoons, may not be seen easily, and the child may choose to watch programmes in which there is less movement, like panel games. Children with ocular motor apraxia may choose to get close to the television. This does not cause any harm.

Some things, which are moving quickly, may not be spotted because the ability to locate and follow moving targets is reduced. It is important to teach how to cross roads safely. Ball sports can also be difficult. When a child is old enough it is worth practicing throwing and catching.

A child who chooses to use head thrusts should not be made to stop doing this. They are trying to improve their vision and are often doing it without knowing it.

Difficulties at school may be due to some of the reading books being hard to see. This often means it takes longer and more effort to do the work. If the size of print is increased most children find schoolwork easier. They may also benefit from using a computer software programme while reading. The programme only shows one word of a sentence at a time. It is in the middle of the computer screen. This reduces the need for fast saccadic eye movements. It can increase reading speed and reduce tiredness.

Even if a child has very poor vision many useful and practical things can be done to help.

Who wrote these documents?

These pages are the consensus of opinion of many different people. They include parents of visually impaired children, visually impaired children themselves, Community Paediatricians, Ophthalmologists, Educationalists and Psychologists.

The main author and person responsible for their content is Dr Andrew Blaikie who was an Ophthalmology Research Fellow with Visual Impairment Scotland and is a member of the Royal College of Ophthalmologists.

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