Eye Conditions

by Dr Andrew Blaikie for VI Scotland

Medical Information On Albinism

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.

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 Albinism

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 optic nerves join together about halfway between the eyes and the brain and then splits apart again. This join is called the optic chiasm. At the optic chiasm about half of the visual information in each optic nerve swaps over to the opposite nerve. This swap makes it easier for the brain to make sense of all the visual information. The information then travels to many different special ‘vision’ parts of the brain. All the parts of the brain and eye need to be present and working for us to see normally.

What is Albinism?

The colour of our skin depends on how much melanin is in it. Melanin is a dark brown material (pigment) found in many parts of the body. The body parts that it helps colour include the skin, hair and eyes. Some children cannot make as much melanin as others and some cannot make any melanin at all. They may have pale skin and blonde hair with light coloured eyes. These children have Albinism. They usually also swap more information at the optic nerve join (chiasm) than normal. This can affect the way the see. Children are born with Albinism. They cannot ‘catch’ it in later life.

Why Are Some Children Unable To Make Melanin?

Albinism is 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. A child with Albinism 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. If a certain gene has a mistake in it then a special chemical called an enzyme may not work correctly. These enzymes are needed by the child to help make melanin. In children with Albinism they either don’t have as much of the special enzyme that helps them make melanin or they have none at all.

There are many different ways a child can ‘inherit’ a condition. See the VI Scotland Document on ‘Ways Children Can Inherit Eye Conditions’.

There Are Different Types Of Albinism

There are many different types of Albinism. It can seem very complicated. Most experts would say there are three main types of Albinism that vary by:

• Which parts of the body are mainly affected
• How much melanin the child makes
• Whether the child has any other associated conditions.

The three main types of Albinism are called:

• Oculocutaneous Albinism (affects the eyes and the skin)
• Ocular Albinism (only affects the eyes)
• Albinism Associated With Other Conditions

Oculocutaneous Albinism

In Oculocutaneous Albinism both the eyes and the skin are affected. ‘Oculo’ refers to the eyes and ‘cutaneous’ to the skin. There are two main types of Oculocutaneous Albinism that vary depending on how much melanin the child is able to make.

• Tyrosinase Negative Oculocutaneous Albinism

In the first type the child cannot make any melanin at all. This is called ‘Tyrosinase Negative’ Albinism. Tyrosinase is the name of the enzyme that helps the child make melanin. These children do not have a working Tyrosinase enzyme because of a mistake in their genes. These children have white hair and pale skin. The eyes may appear pink or reddish. They also are likely to constantly move in a fast ‘to and fro’ way (Nystagmus). See the VI Scotland Document on Nystagmus. Children with this type of Albinism normally have very impaired vision.

• Tyrosinase Positive Oculocutaeneous Albinism

In the second type of Oculocutaneous Albinism children can make some melanin but not as much as normal. Their hair is blond and their skin is not as pale. Their eyes are usually pale blue. The children normally also have Nystagmus but their vision is not as impaired.

Ocular Albinism

In Ocular (eye) Albinism it is the eyes that are mainly affected. The eyes are affected in the same way as for Oculocutaneous Albinism. The skin usually appears the normal colour for the race of the child or slightly paler. Usually only boys are born with this form of Albinism.

Albinism Can Be Associated With Other Conditions

Very rarely some children are born with Albinism and another condition.

What Types Of Conditions Might Also Affect Children With Albinism

If a child with Albinism bruises easily they may also have a rare condition in which the blood does not clot well, leading to bruising. This is called ‘Hermansky-Pudlak Syndrome’. These children may also become short of breath easily.

If a child with Albinism develops infections more often than is usual they may have a condition called ‘Chediak-Higashi Syndrome’. In this condition children have a lower immunity to infection than other children.

How does Albinism affect the way a child sees?

Albinism can affect vision in different ways in different children. Generally the less melanin pigment in the iris and retina of the child, the poorer their vision is. Some children may see very well while others may only see bright lights and large shapes. In Albinism it is usually only the central vision that is poor. The vision around the sides is often fine. Because of this although many children with Albinism have difficulty seeing small letters most have no difficulty seeing to get around.

In children with Albinism the iris is usually pale and thin with gaps in it. Because of this more light than usual gets into the eye. The extra light that gets into the eye scatters around the inside causing blurred vision. Because too much light enters the eyes, children with Albinism nearly always dislike bright light. This is called photophobia.

The eyes of children with Albinism tend to make fast ‘to and fro’ movements. This is called Nystagmus. Because the eyes are constantly moving, like camera shake, this also leads to blurred vision.

Children with Albinism often need spectacles to help see more clearly. Children may also later develop a squint or a lazy eye.

How is Albinism Diagnosed?

Because the eyes, and often the hair and skin, are paler than normal a diagnosis can usually be made quite easily. An Eye Doctor can examine the child, and often their parents as well, and confirm the diagnosis. The iris often is pale blue or pink with gaps in it. The eyes often move quickly ‘to and fro’ (Nystagmus). Looking at the back of the eye with a special torch the retina often looks paler than normal. All these signs help an Eye Doctor to make a diagnosis.

If there is no family history of Albinism and the child is only mildly affected other tests can be done to help make a diagnosis. These include special electrical tests or scans of the head.

What can be done to help?

There is no known way to help children make more melanin. Lots of things can be done though to help children with Albinism. Bright light often causes discomfort and reduced vision (photophobia). A sunhat and sunglasses may help reduce the symptoms of photophobia. Special lenses that get darker in brighter light (photochromic lenses) are useful. Sun block cream should be rubbed into paler, exposed skin to avoid sunburn.

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 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 Albinism 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. See the ADVICE section on the VI Scotland website.