Visually Impairing Conditions
by Dr Andrew Blaikie for VI Scotland
Medical Information on Bull's Eye Maculopathy
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
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
Edinburgh EH8 8AQ
Telephone Number : 0131 651 6078
Fax Number : 0131 651 6502
Textphone : 0131 651 6067
Medical Information on Bull's Eye Maculopathy
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. There are two types of photoreceptors named by their shape when looked at in fine detail. They are called 'rods' and 'cones'.
Rod and cone photoreceptors are good at seeing different things
Rods are good at 'seeing':
- things that move
- in the dark
- but only in black and white
- and in less detail.
Cones are good at 'seeing':
- things that are still
- in daylight
- in colour
- and in fine detail.
The covering of rod and cone photoreceptors at the back of the eye makes a thin film called the retina. The central bit of the retina is made up of cones. They help us see the central bit of vision that we use for reading, looking at photographs and recognising faces. The area of the retina around the central bit is made up of rods. The rods see the surrounding bits of vision and help us to walk around and not bump into things especially in the dark. 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 Bull's Eye Maculopathy?
Bull's Eye Maculopathy is the name given to the way the central bit of the retina looks in many different kinds of eye conditions. It is not a diagnosis. It is the description of an appearance of the retina. Using a special instrument the eye doctor can look at the optic nerve and retina at the back of the eye. In children with certain eye conditions these parts of the eye look different from normal. Often the central bit of the retina (the macula) can appear to have circular bands of different shades of pink and orange. Eye doctors often describe this appearance as 'Bull's Eye Maculopathy'.
In what eye conditions may Bull's Eye Maculopathy be seen?
There are many different kinds of eye conditions that can give the appearance of a Bull's Eye Maculopathy. Some of these conditions include:
- Progressive Cone Dystrophy
- Rod-Cone Dystrophy
- Benign Concentric Macular Dystrophy
- Stargardt's Disease
- Batten's Disease
Most of these eye conditions are linked by a problem with photoreceptors in the retina. The photoreceptors either do not work from the day a child is born (stationary) or else slowly stop working during childhood (progressive). This usually leads to blurred vision, poor colour vision and a dislike for bright light (photophobia). Dystrophy is a word for a disease, which a child is born with. Some of these conditions do not only affect the eye but may also affect the rest of a child's body. See the VI Scotland Documents on these other conditions.
Why do some children have eye conditions with Bull's Eye Maculopathy?
There are many different causes of Bull's Eye Maculopathy. Sometimes nobody can say for sure what the cause is. When no cause can be identified this is called Idiopathic. Most maculopathies are caused by a mistake in the child's genes. Genes are a chemical alphabet stored in the body. Genes contain the body's "built-in" plan to make sure all the parts of the body work correctly. If a gene has a mistake in the chemical alphabet then a part of the body may not work correctly. Sometimes many parts of the body do not work correctly. A child with Bull's Eye Maculopathy has often been passed (inherited) a gene with a mistake in it from one or both parents. Sometimes by chance a new mistake occurs in the child's genes and the parent's genes are normal. There are many different ways a child can 'inherit' a condition. See the VI Scotland Information Document on 'Ways Children Can Inherit Eye Conditions'.
How is the diagnosis made?
A young child may complain of blurred vision. The school nurse or orthoptist may also note poor vision during screening programmes. Sometimes parents 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 check the way the eyes behave to bright lights. If the pupils of a child move slowly to a bright light then a there is likely to be a condition of the retina or optic nerve. Using a special instrument the eye doctor can look at the optic nerve and retina at the back of the eye. In children with eye conditions sometimes these parts of the eye look different from normal. Often the central bit of the retina (the macula) can appear to have circular bands of different shades of pink and orange. Eye doctors often describe this appearance as 'Bull's Eye Maculopathy'.
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. The record of the signals will help the doctors decide what the matter is. This test is called an Electroretinogram (ERG).
Sometimes it is not only vision yhat is affected
Some eye conditions with Bull's Eye Maculopathy may present initially with symptoms that have nothing to do with vision. Conditions such as Batten's Disease may present with increasing difficulty handling objects, increasing clumsiness moving around, gradual change in mood and personality, decreased attention span, slurred speech and poor memory. It may be only later that a problem with vision is noticed.
How does Bull's Eye Maculopathy affect the way a child sees?
There are many different kinds of eye conditions that can give the appearance of a Bull's Eye Maculopathy. Each different eye condition can affect eyesight in different ways. In some conditions the child's vision can be almost normal. In other conditions vision can be very poor. Sometimes children with Bull's Eye Maculopathy can also have other conditions of their body, not just their eyes.
A child who is born with poor vision will often initially grow up and feel their vision to be 'normal'. At first they assume that everyone else has vision the same as their own, as they have never known anything else but their own visual world. They do not realise that other people see things differently.
Older children who develop problems with their vision will however slowly notice problems such as:
- Blurred vision, especially in the central bit of vision
- Dislike of bright light (photophobia)
- Poor colour vision
- Fast to-and-fro movements of the eyes (nystagmus)
Is there any treatment for Bull's Eye Maculopathy?
There is no good way to treat inherited genetic eye conditions that cause Bull's Eye Maculopathy. Usually there is also no good way to stop the sight loss that often occurs along with Bull's Eye Maculopathy. But many things can be done to help visually impaired children.
What can be done to help?
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. This will help the child see more clearly and reduce glare and photophobia. It will also help the vision parts of the brain to grow and develop correctly.
Most children with Bull's Eye Maculopathy 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 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.