University of Edinburgh
 

Medical Information on Nystagmus

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 Nystagmus

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 Nystagmus?

Our eyes move quickly when we watch something that is moving quickly. Our eyes are still when we look at something that is still. This is so the eyes can focus sharply on an object. The eye can then give clear signals to the brain to make clear vision. In some children the eyes are always moving to-and-fro even though the object that they are looking at is still. This to-and-fro movement is called Nystagmus. Children do not know that they are doing it. Because the eye is shaking the vision is usually a bit blurred. This is like if a camera moves during a photograph. The photograph is also usually blurred. The to-and-fro movements are usually from left to right and back but it can be in any direction. The movements of the eyes can be large or small and fast or slow.

What is the cause of Nystagmus?

There are three main causes of Nystagmus.

  1. Reduced vision is the most common cause of nystagmus
  2. Children with reduced vision often develop Nystagmus. This is the most common cause of Nystagmus in children and is called Sensory Defect Nystagmus (SDN). Albinism is an example of this.

  3. Some children are born with nystagmus
  4. The second most common type of Nystagmus is known as Congenital Idiopathic Nystagmus (CIN). Children are born with this condition. This is what Congenital means. The parents usually notice it in the first few months of a child's life. Nobody knows what the cause is. Idiopathic is a medical word used when nobody understands the cause of a condition. Congenital Idiopathic Nystagmus may occur by chance but it often runs in families. One parent may be affected and other children may also be born with the condition.

  5. A bit of the brain that controls eye movements may not be working
  6. Sometimes the parts of a child's brain that help the eyes to move smoothly do not work. This causes the eyes to move in a fast, jerky to-and-fro way. This is known as Neurological Nystagmus (NN).

How does Nystagmus affect the way a child sees?

You might expect Nystagmus to cause vision to shake and move to and fro as well. This does not usually happen in children because the brain ignores the shaking. However the to-and-fro movements have the same effect as camera shake might have on a photograph. The picture is blurred. In Congenital Idiopathic Nystagmus the to-and-fro movements of the eyes are usually greater when looking into the distance and are less when looking at something up close. This causes the vision in the distance to be more blurred than for near. The amount of wobble can be less when the eyes look to the side. For this reason some children with Congenital Idiopathic Nystagmus turn their heads to one side especially when they want to see something small. This reduces the wobbling of the eyes and improves vision. Vision can also vary with a child’s emotional state. For example, the to and fro movements can become bigger and faster when a child is stressed, tired or nervous.

Sometimes children with Nystagmus wobble their heads from side to side. Children also do this to try to get better vision. The amount of blurring of vision varies between children and also depends on the cause of the Nystagmus. In some children the nystagmus may slowly get less and their vision will get better. In other children the reduced vision stays and magnifying aids are needed to read. It is difficult to say which will happen.

How is Nystagmus diagnosed?

Often parents will notice that their child's eye 'shimmer' and 'shake'. Sometimes parents also notice (by the way their child acts) that their child's vision is reduced. If they discuss their concerns with their Family Doctor an assessment can be arranged.

An eye doctor can then examine the child's eyes and decide if other tests are needed. The eye doctor will be interested to examine the eyes of the parents and other children in the family. This is to see if it is the child has Congenital Idiopathic Nystagmus. That is the type of Nystagmus that tends to run in families.

There are also special tests that can be done to help the eye doctor decide what is wrong. These tests measure signals from the eyes when a child is shown a bright light. Sticky patches are placed around the eyes. The sticky patches are attached to wires that lead to a machine. The machine records the electrical signals made by the eyes. This test is called an Electroretinogram (ERG). The record of the signals helps the eye doctor decide if the child has Sensory Defect Nystagmus (SDN).

In some eye clinics a test that records the pattern of the child's eye movements can be done. Some types of Nystagmus always make a specific pattern. This can be very helpful to decide what the cause of the Nystagmus is.

Rarely the eye doctor might arrange for the child to have a Brain Scan. This test will help to decide if the child has Neurological Nystagmus (NN).

What can be done to help?

Sometimes spectacles with special lenses called prisms can be worn. They can reduce the eye wobble and improve vision.

In a small number of children with an obvious head turn it is possible to do an operation to help. The muscles that move the eyes are adjusted so that the head turn and eye wobble are reduced.

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

We use our vision to get around, learn new things and to meet other people and make friends.

Most children with Nystagmus 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 some of their own personal difficulties with vision.

A child who chooses to use a head turn or to move the head to and fro to improve vision should not be made to stop doing this. They are trying to improve their vision and are often doing it without knowing it. It is important that they are placed in the class to let them use this head posture to their best advantage. Let a child hold a book very close if it helps them see better. Because of this it is often impossible to 'share' books and read together at the same time. Two copies of the same book are really needed to allow reading together.

Problems 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 will find schoolwork easier. Sometimes placing reading books on a slope, which tilts the print towards the child, will improve reading speed as well.

When reading it can be helpful to read one line at a time through a ‘letter box’ placed over the page. Placing a piece of blue tack below the line they are reading, at the beginning of the next sentence, can help some children find their way back to the start of the next line more quickly.

It is also worth watching carefully to find out what the smallest toys are that a child can see and play with. Then try to only play with toys that are the same size or bigger. Placing one toy on a plain background will often help children see it more readily. Placing lots of toys of different size and colour close together on a patterned background can sometimes make them even more difficult to see.

Recognising facial expressions can often be difficult. It is worth trying to find out at what distance facial expressions can be seen and responded to. Then always try to talk and smile from within this distance. This helps a child to learn what facial expressions mean and to copy them.

Even if a child has very poor vision many useful and practical things can be done to improve the ability of the child to get around, interact with other children and learn.

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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