Visually Impairing Conditions
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?
- Parents' Support Group
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. It is not a means to access a 'second opinion' particularly in any medico-legal cases. 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
Due to staffing limitations we are not able to offer telephone or email advice to parents of children who are not notified with VI Scotland.
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.
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
What we see is made in the brain from signals given to it by
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 focusing 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. All parts of the brain and eye need to be present and working for us to see normally.
Rarely the cornea may becomethin and stretched. This causes the cornea to change shape and instead of having an even curved dome surface becomes an uneven cone shape. The light entering the eye no longer focuses accurately on to the retina and the vision becomes blurred. This is what happens in keratoconus.
Most cases of Keratoconus occur by chance. Keratoconus occurs more commonly in children who rub their eyes and suffer from eczema. It is also more common in children with Down's syndrome.
Rarely the condition may run in families. There is a 1 in 10 chance that a person with Keratoconus would have a child with the same condition.
Keratoconus can affect vision in different ways depending on the level to which the corneas are affected by the thinning and stretching. Initially the vision becomes blurred. Sometimes this is associated with sensitivity and aversion to bright lights.
Spectacles or contact lenses will initially improve the vision and in most patients this is all that is needed. The condition usually affects both eyes but may affect one eye less than the other and occasionally not at all.
In some children the condition progresses and the cornea becomes more uneven and cone shaped until neither spectacles or contact lenses can improve the vision. At this stage the cornea may have developed scarring and become hazy. To improve vision now a replacement cornea is needed. This requires an operation.
Keratoconus can be diagnosed during an examination by an ophthalmologist. Using a special piece of equipment called a slitlamp the ophthalmologist can see clinical signs that are only seen in Keratoconus. To help confirm the diagnosis sometimes a picture is taken of the cornea using a special camera which measures how curved and uneven the cornea has become.
We use our vision to get around, learn new things and to meet other people and make friends.
It is important that children are encouraged to wear their spectacles or contact lenses. This will help the child see more clearly and may reduce glare and photophobia. It will also help the vision parts of the brain to grow and develop correctly.
Most children with Keratoconus 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.