Eye Conditions

by Dr Andrew Blaikie for VI Scotland

Medical Information On Aicardi's Syndrome

For whom is this information intended?

The information contained in this document is intended for use primarily by parents, other members of the family and older children with visual impairment. The information will also be of use to interested health professionals, carers and teachers.

The purpose of each information document

The purpose of the information is to explain:

• The way the eyes and brain normally work to make 'vision'
• The reason why vision may become impaired by a specific condition
• The cause of the condition
• The effects of the condition on the child's vision
• How the condition is diagnosed
• What can be done to help

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. Inevitably there will be some mistakes. We apologise for this.

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

After reading the information we hope you will:

• 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

Authors

These pages represent the consensus of opinion of many different people who 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 is an Ophthalmology Research Fellow with Visual Impairment Scotland and a member of the Royal College of Ophthalmologists. We are very keen that parents and children feedback to VI Scotland about these information documents. If you have any questions or comments regarding the information please contact:

Visual Impairment Scotland
Scottish Sensory Centre
The University of Edinburgh
Holyrood Road
Edinburgh EH8 8AQ

Telephone Number : 0131 651 6078
Fax Number : 0131 651 6502
Textphone : 0131 651 6067

Email : viscotland@ed.ac.uk

Website : www.viscotland.org.uk

Medical Information On Aicardi's Syndrome

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. Although the brain works for all the body, about half of the brain is used just for vision. The brain is split into two halves, a right and left half. These halves are joined by a large bundle of wires known as the corpus callosum. All parts of the brain and eye need to be present and working for us to see normally.

What is Aicardi’s Syndrome?

Very rarely when a baby is growing in the womb not all of the parts of the eye and brain grow correctly. If a part of the body does not grow at all then this is known as agenesis. In Aicardi syndrome several parts of the eye and brain do not grow fully and some parts do not grow at all. Commonly the parts that fail to grow include:

• Patches at the back of the eye
• The large connection between the two halves of the brain (corpus callosum)
• Areas of the brain normally used for vision, speech and controlling the arms and legs.

Genes hold the ‘Plan’ for the body to grow in the womb

The body has a ‘built-in plan’ to make sure all the parts of the body grow fully and correctly while in the womb. This plan is written in our genes. Genes are a chemical alphabet held in every cell of the body. Genes are stored as long threads folded up into thick ropes called chromosomes. Every cell of the body has exactly the same number and kind of chromosomes. There are 23 different chromosomes with each chromosome also having a copy of itself so that there are 46 in total (23 pairs). One pair of chromosomes are called the sex chromosomes and hold the plan for making an unborn baby grow into a boy or a girl. There are two types of sex chromosomes called X and Y. The letters just describe the shape of the chromosome when seen in fine detail. If an unborn baby has an X and a Y sex chromosome then they will develop into a boy (XY). If the sex chromosomes are both X then they will develop in the womb into a girl (XX).

What is the cause of Aicardi’s Syndrome?

All cases of Aicardi’s syndrome occur by chance. There is no evidence that the condition runs in families or is caused by prescription or recreational drugs.

The condition only occurs in girls and this seems to be due to part of an X chromosome not working correctly. Girls normally have two working X chromosomes. In Aicardi’s syndrome one X chromosome in the pair has a mistake in the ‘plan’ and does not work correctly. The effect on the development of the unborn girl leads to parts of the eye and brain not growing correctly to the usual ‘plan’ in the womb. No boys are ever born with this condition.

How does Aicardi’s Syndrome affect a child?

The main symptoms are due to the eyes and brain not developing correctly in the womb. The number of symptoms and the degree to how they affect a child are related to the level of development of the eyes and brain. The most common effects are the development of:

• Epilepsy
• Learning difficulties
• Poor mobility
• Poor vision

The epilepsy usually starts in the first six months of life. Occasionally there can be other associated physical signs such as cleft lip and palate and a more curved backbone than usual (scoliosis).

How does Aicardi’s Syndrome affect a child’s vision?

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.

Aicardi syndrome can affect vision in different ways depending on the degree to which the eyes and the brain are affected. If only mildly affected then the overall vision may be good enough for the child to see and understand large print and easily recognise faces. However because in Aicardi syndrome the eye and brain are usually both affected to a severe level, vision can be very poor. The child may have reduced sharpness of vision and may only see bright lights and large shapes. The poor vision may be more marked if this is combined with learning difficulties as well. Sometimes children can develop fast ‘to and fro’ movements of the eyes (Nystagmus) or a Squint. See the VI Scotland Documents on these conditions.

Are there any conditions associated with Aicardi’s Syndrome?

Sometimes other parts of the brain do not grow correctly when the baby is in the womb. In very rare cases a small gland in the brain, which makes hormones (the pituitary gland) does not develop and function correctly. If a child is not increasing in height and gaining weight normally then tests can be done to decide if extra hormonal treatment is needed.

How is Aicardi’s Syndrome diagnosed?

If Aicardi syndrome is suspected then a brain scan may show some of the typical development changes such as the absence of the corpus callosum. A measurement of the electrical signals from the brain (EEG) may also show characteristic findings of Aicardi’s syndrome.

How can doctors help?

Sometimes spectacles will help to improve vision. Special low visual aids (LVAs) may also help.

Epilepsy can be treated with tablets. Physiotherapy and occupational therapy can help improve mobility. Occasionally conditions where certain hormones are lacking can be associated with Aicardi’s syndrome. These conditions must be recognised and treated by a specialist children’s doctor (paediatric endocrinologist).

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 socialise.

Most children with Aicardi’s syndrome have difficulty getting around because of poor leg and arm control and reduced vision. It is important to recognise their particular limitations of vision and mobility.

If your child has been prescribed spectacles it is important that they are encouraged to wear them. This will help the child see more clearly and help the vision parts of the brain to grow and develop correctly.

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, especially if they also use their LVA. If a child has been given an (LVA) then they should be encouraged to use it.

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. See the ADVICE section on the VI Scotland website.