University of Edinburgh
 

Medical Information on Retinitis Pigmentosa

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 Retinitis Pigmentosa

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 Retinitis Pigmentosa?

Retinitis Pigmentosa is the name given to a wide range of eye conditions. 'Retinitis' means disease or inflammation of the retina. 'Pigmentosa' refers to how the retina can look in this condition (the retina can often develop lots of small, dark specks of pigment). Retinitis Pigmentosa eye conditions are all linked by a problem with the rod and cone photoreceptors. The photoreceptors either work poorly from the day a child is born or else slowly stop working over a period of time. Usually the rods are affected more than the cones. Some Retinitis Pigmentosa conditions do not only affect the eye but may also affect the rest of a child's body.

What are the causes of Retinitis Pigmentosa?

There are many different causes of Retinitis Pigmentosa. Sometimes nobody can say for sure why a child has Retinitis Pigmentosa. When no cause can be identified this is called Idiopathic.

There are many reasons why a child might develop Retinitis Pigmentosa

Retinitis Pigmentosa is caused by a misprint 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 misprint 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 Retinitis Pigmentosa has often been passed (inherited) a gene with a misprint in it from one or both parents. Sometimes by chance a new misprint 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'.

What are the names for some of the more common types of Retinitis Pigmentosa?

Rod-cone Dystrophy, Leber's Amaurosis, Usher's Syndrome and Batten's Disease are the names of some of the more common conditions where rod and cone photoreceptors do not work properly.

How is the diagnosis made?

Young children with Retinitis Pigmentosa may develop:

  • Fast to-and-fro movements of the eyes called Nystagmus.
  • 'Roving' eye movements where the eyes appear to slowly wander around not fixing and staying still on any objects.
  • 'Eye Poking' where the child touches their eyes with their fingers.

Parents will often notice these signs. 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 check the way the eyes behave to bright lights. If the pupils of a child move slowly to a bright light then Retinitis Pigmentosa is more likely. Using a special instrument the eye doctor can look at the optic nerve and retina at the back of the eye. In children with Retinitis Pigmentosa sometimes these parts of the eye look different from normal.

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. If the signals are weak or absent then Retinitis Pigmentosa is more likely. This test is called an Electroretinogram (ERG).

Some children with Retinitis Pigmentosa may present initially with symptoms that have nothing to do with vision. Conditions such as Batten's Disease may present with 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 also noticed.

How does Retinitis Pigmentosa affect the way a child sees?

Retinitis Pigmentosa can affect different children in different ways.

Most young children who are born with rod and cone photoreceptors that do not work 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. Most Retinitis Pigmentosa conditions however become worse as the years pass.

Some older children may begin to notice that their vision is blurred around the edges and that their vision is especially poor in the dark. These children might mainly have a problem mainly with their rod photoreceptors.

Some other children may notice that their central vision is becoming increasingly blurred and that most colours are not bright. These children may mainly have a problem with their cone photoreceptors.

Some other children may end up only seeing bright lights or the movement of large objects. These children may have problems with both cone and rod photoreceptors.

Sometimes in adulthood cataracts can develop. Cataract is when the normally clear lens of the eye becomes hazy. If the lens is not clear then not all the light can get into the eye and vision is often blurred. This can be treated by an operation. The hazy lens is removed and replaced by a clear plastic one. See the VI Scotland document on this condition.

Are there any other conditions associated with Retinitis Pigmentosa?

Some children with Retinitis Pigmentosa only have visual impairment. Many other children may have other conditions such as:

  • Poor Hearing
  • Learning Difficulties
  • Reduced Growth

The other associated conditions depend on the cause of the Retinitis Pigmentosa.

What can be done to help?

At present there is no good way to stop the sight loss in Retinitis Pigmentosa. But many things can be done to help children with this condition.

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

It is important however to be aware of your child's special problems with vision.

It is important that children are encouraged to wear their spectacles or Low Vision Aids (LVA). 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.

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.

Many children with Retinitis Pigmentosa need early and specialist care from the local visual impairment support team. 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 worked as an Ophthalmology Research Fellow with Visual Impairment Scotland and is a member of the Royal College of Ophthalmologists.

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