University of Edinburgh
 

Medical Information on Chorioretinal Atrophy

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 to 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 Chorioretinal Atrophy

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. The retina lies on a layer of nerves and blood vessels. This layer is called the choroid. The retina needs a healthy choroid to work. 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. All parts of the brain and eye need to be present and working for us to see normally.

What Is Chorioretinal Atrophy?

Atrophy is the medical word for when a bit of the body withers away and stops working. Chorioretinal is one big word often used to describe the choroid and retina together.

Chorioretinal Atrophy is a condition of the eye where both the choroid and retina are damaged. This causes them to wither away and stop working.

What are the causes of Chorioretinal Atrophy?

There are many different causes of Chorioretinal Atrophy.

Infection is the most common cause of Chorioretinal Atrophy

The most common reason for the choroid and retina to become damaged is by an infection. There are many different kinds of germs that can cause infection. They all have complicated names and include:

These germs usually only damage the eye if they cause an infection in an unborn baby. This means that the baby may be born with visual impairment. Sometimes as well as causing Chorioretinal Atrophy the germs may cause damage to other parts of the eye. This may lead to other eye conditions such as cataract, iritis or glaucoma. See the VI Scotland information on these conditions. The infection may also affect other parts of the body. This may lead to the child developing epilepsy, reduced hearing or learning difficulties.

Myopia (short-sight) sometimes leads to Chorioretinal Atrophy

Myopia is also known as 'short-sight'. This means that a child who is 'short-sighted' can see better at 'short' distance than 'long'. These children usually have larger eyes than usual. Some children with myopia can develop Chorioretinal atrophy when they are older.

Inflammation may also damage the Choroid and Retina

Sometimes children can develop inflammation of the choroid and retina. The inflammation may be caused by the child's own immune system. The immune system usually helps to fight infections. Very rarely it may 'attack' bits of a child's own body. These children may also have an inflammatory condition of their blood vessels (vasculitis) or joints (arthritis). 'itis' means 'to be inflammed'. 'itis' is often added to end of the name of a part of the body to describe an inflammatory condition of that part. The 'posterior uvea' is another medical name for the choroid. When the choroid is inflammed it is often called posterior uveitis. Posterior uveitis is a cause of Chorioretinal Atrophy.

Often no cause can be identified

Often it cannot be said for sure why the choroid and retina becomes damaged. Doctors call this Idiopathic Chorioretinal Atrophy.

How does chorioretinal atrophy affect the way a child sees?

Most young children will feel their vision to be 'normal' as they have never known anything else but their own visual world. At first they assume that everyone else has vision the same as their own. They do not realise that other people see things differently.

Chorioretinal Atrophy may affect any part of the back of the eye. Some conditions such as toxoplasma tend to cause scarring of the central bit. If this happens then the central part of the vision will also be missing. This causes reduced vision. The child will not usually notice if a part of the retina away from the centre is scarred.

Toxoplasma can affect one or both eyes. If the central bit of the retina and choroid in both eyes is damaged then the child will notice blurred vision. The vision around the sides will still be OK. This vision is useful for getting around and not bumping into things. The child will however have difficulty reading and recognising faces. Sometimes fast to-and-fro movements of the eyes occur. This is called Nystagmus. Squint may also develop. See the VI Scotland information on these conditions.

How is the diagnosis made?

An eye doctor can recognise the typical pattern of damage at the back of the eye. Sometimes blood tests and scans of the eyes and brain may also help.

What can be done to help the eyes?

Once Chorioretinal Atrophy has developed it does not get better. The retina cannot grow back and fix itself. Usually the damage does not get any worse. Sometimes germs like toxoplasma can stay 'asleep' in the retina for many years and 'wake up' at any time. If it 'wakes up' a new infection can start. Blurred vision and 'floaters' are common symptoms of a new infection. It is important to treat any infection quickly to prevent further damage to the retina. Antibiotics and steroid tablets are often used. If treated quickly the blurred vision and floaters usually settle within a few weeks. In some cases the jelly in the eye (vitreous) can become inflammed. This can cause annoying 'floaters' that get in the way of vision. In most children the floaters gradually go away with treatment.

Vision can be improved with the use of Low Vision Aids and increasing the size of print.

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

In some children there is a small risk of more parts of the retina and choroid becoming damaged. This may lead to further blurred vision. If a child notices this then they should see an eye doctor as soon as possible. Recurrent inflammation rarely affects both eyes at the same time.

If vision is reduced in both eyes it is important to understand how the child sees and to make up for this. We use our vision to get around, learn new things and to meet other people and make friends.

Most children with Chorioretinal Atrophy 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.

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.

It is 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.

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 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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