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Aniridia

Who is this information for?

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

This information should help you to understand:

  • 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

What this information is not for

This information is not a substitute for a consultation with a health professional and should not to be used as a means of diagnosing a condition.

Medical information on aniridia

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)

Image of diagram of the structure of the eye including labels for lens, cornea at the front and retina at the back

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.

What is aniridia?

Very rarely when a baby is growing in the womb not all of the parts of the eye grow. If the iris fails to grow then this is known as aniridia. In some children only some parts of the iris fail to grow and the condition is called ‘partial’ aniridia.

Image of a child with aniridia and one with partial aniridia

What is the cause of aniridia?

The condition may run in families. A child can inherit aniridia from a parent who also has the condition. Rarely it may occur for the first time in a family as a result of marrying a cousin or a more distant relative. About one third of cases of aniridia occur by chance.

There is no evidence that aniridia is caused by any prescription or recreational drugs or chemicals in the environment.

How is the diagnosis made?

Aniridia can be diagnosed during an examination by an ophthalmologist. Using a special piece of equipment called a slit lamp, the ophthalmologist can see that parts of the iris are missing.

How does aniridia affect the way a child sees?

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.

Aniridia can affect vision in different ways depending on the level to which the iris is affected and if there are other problems with the eyes. Both eyes are usually affected but one eye may be less affected than the other.

If a large part of the iris is missing then the sharpness of vision may be reduced so as they may not see so clearly. This is because the normal iris and pupil reduce the amount of light entering the eye and help the lens to focus light to the back of the eye (retina). Without an iris too much light gets into the eye. This may cause glare and dazzle especially on sunny days.

Without an iris the light will not focus sharply onto the back of the eye. This causes blurred vision. Usually children with aniridia can develop fast ‘to and fro’ shaking movements of the eyes called nystagmus. This ‘camera shake’ can also reduce sharpness of vision. Vision can often be improved by wearing spectacles that focus the light more sharply on to the back of the eye. Adding a tint to the lenses can reduce glare and dazzle.

Other parts of the eye can be affected in children with aniridia

The pressure inside the eye can be higher than normal. The high pressure may damage the wires that join the eye to the brain (the optic nerve). This is called glaucoma. In later life this can lead to poor vision. The pressure usually reduces with drops or an operation (trabeculectomy). This prevents further damage to the optic nerve.

The cornea (clear window at the front of the eye) is the other part of the eye that can be affected. Later in childhood the skin on the surface of the cornea can begin to fail. This can make the surface of the cornea bumpy and irregular. This can make the eye uncomfortable and more sensitive to light (photophobic). It can also lead to infection on the surface of the eye and scarring. This means that vision can become worse later in childhood. Lubricating and antibiotic drops can help make the eye more comfortable. Sometimes an operation can help to improve the surface of the eye and make vision better. The aim of an operation would be to replace the hazy cornea with a new clear one (corneal graft operation). Sometimes it is also necessary to replace ‘stem cells’ at the edge of the cornea. These help keep the skin on the surface of the cornea healthy.

The lens in children with aniridia can become less clear in time. When a lens becomes less clear this is known as a cataract. The cataract can be removed and replaced with a clear plastic one. This operation can improve vision.

An eye with aniridia can sometimes have fewer wires joining it to the brain. This is known as optic nerve hypoplasia. This can lead to poor vision.

A child with aniridia needs regular check ups with an eye doctor to identify any of these conditions and to treat them if they arise.

Are any other conditions associated with aniridia?

About one third of cases of aniridia occur by chance. These children have a 1 in 4 chance of developing a tumour of the kidney. In most cases a special blood test can tell which children are most at risk. The children most at risk need regular examinations of the kidneys so that if a tumour does develop it can be treated promptly. Children with aniridia that runs in families are not at risk of developing a tumour of the kidney.

How can parents, family, friends and teachers make a difference?

Make sure that your child attends all appointments, and make sure that any treatment is carried out as instructed.

If your child has been prescribed spectacles, contact lenses or a low visual aid (LVA) it is important that they are encouraged to wear and use them. This will help your child see more clearly and ensure the vision parts of the brain grow and develop correctly.

Be aware that adjusting to daylight in the morning can be uncomfortable. Sometimes this is painful and the eyes may water a lot.

Be aware of the problems with glare. Children may need reduced or shaded light. Blinds and curtains are useful. Wearing a hat and tinted glasses can also help reduce symptoms of light sensitivity (photophobia). Wherever possible use matte surfaces for desktops, whiteboards, paper, wall, floors and so on. Shiny surfaces, snow and water can reflect light causing glare.

If your child has also been prescribed drops they should be used regularly as advised by the nurses and doctors at the eye clinic.

We use our vision to get around, learn new things and to meet other people and make friends. Most children with corneal dystrophy 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, especially if they also use their LVA. If a child has been given an LVA then they should be encouraged to use it.

  • Near work – a close reading position may be preferred and should not be discouraged.
  • Seating in school – where possible your child should be seated close to the teacher, away from windows if there are no blinds and close to the board and television.
  • School equipment – children may benefit from using some type of magnifier. This enlarges print making reading less tiring. It may sometimes be helpful to provide a desk stand or a copyholder, which will bring work to eye level and prevent discomfort and poor posture.

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.

Note on the above information

Information:

This information is intended to describe most aspects of the condition but each child is different and there will always be exceptions.

This information 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.

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. 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
Tel: 0131 651 6078
Textphone : 0131 651 6067

Useful contacts

The Orthoptic Department at Sheffield Children’s Hospital

0114 271 7468 or 0114 2717481

Sheffield Royal Society for the Blind

Advice and support for children of all ages with a vision problem
5 Mappin Street, Sheffield, S1 4DT
0114 272 2757
www.srsb.org.uk

Sheffield Specialist Support Services and Visually Impaired Service

Advice and support for children of all ages with a vision problem
0114 239 8336

RNIB

0845 766 9999
www.rnib.org.uk

LOOK (For families with visually impaired children)

0121 428 5038

Tadpoles (International Glaucoma Association)

108c Warner Road, London, SE5 9HQ
020 7737 3265
www.iga.org.uk
info@iga.org.uk

Specs

PO Box 118, Westerham, TN16 3WR
01959 570142
www.eyeconditions.org.uk

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Disclaimer

Please note this is a generic information sheet relating to care at Sheffield Children’s. The details in this resource may not necessarily reflect treatment at other hospitals. This information is not intended as a substitute for professional medical care. Always follow your healthcare professionals’ instructions. If this resource relates to medicines, please read it alongside the medicine manufacturer’s patient information leaflet. If you have specific questions about how this resource relates to your child, please ask your doctor.

Resource number: EYE14

Resource Type: Article

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