Coloboma

This resource about coloboma will 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 resource is not a substitute for a consultation with a health professional and should not be used as a means of diagnosing a condition.

What is a coloboma?

Very rarely when a baby is growing in the womb, not all of the parts of the eye grow fully. If a part of the eye does not grow as it should, it is called coloboma.

Coloboma is a Greek word. It means ‘curtailed’ or ‘unfinished’. The parts that sometimes do not grow fully include the iris, lens, retina or optic nerve.

What is the cause of coloboma?

Most cases of coloboma occur by chance. No reason or cause for it happening can be identified. This is called ‘sporadic’.

Sometimes the condition runs in families. This is called autosomal dominant inheritance. An eye doctor should examine all the close relatives of a child with coloboma. Sometimes mild types of coloboma can be found in a parent or sibling of an affected child. This may help the doctors say if coloboma is likely to occur again in the same family.

Very rarely it may occur for the first time in a family as a result of marrying a cousin or even a more distant relative. This is called recessive inheritance. It is just something that can happen.

Most children with coloboma in only one eye usually have good vision in the other. These children do not normally complain of reduced vision. When both eyes are affected the child is much more likely to have blurred vision. This resource mainly refers to children with coloboma affecting both eyes.

How might coloboma affect my child’s vision?

Coloboma can affect vision in different ways depending on how affected the eyes are.

If only a small part of the iris is missing then your child’s vision may be normal. If a large part of the retina and optic nerve is missing then your child’s vision may be poor. A large part of the visual world may be missing (visual field loss) and the sharpness of vision may be reduced. Your child like this may only see bright lights and large shapes from the affected eye.

Despite this, young children with large colobomas and visual impairment will at first feel their vision to be ‘normal’. They have never known anything else but their own visual world. They will assume that everyone else has vision the same as their own. They will not realise that other people see things differently.

Fast ‘to and fro’ movements of the eyes can develop. This is called nystagmus. Sometimes a child with coloboma can also develop a squint. This is when the eyes do not look in the same direction. If you wish more information on any of these conditions please ask us.

Are there any other conditions associated with coloboma?

Most children with coloboma are otherwise normal.

Eyes affected by coloboma are often short-sighted (myopic). Spectacles can sometimes help children see more clearly and ensure the vision parts of the brain grow and develop.

Rarely however other conditions of the eye may occur that may cause blurring of the vision and other problems such as:

• microphthalmia (smaller eye)
• cataract (hazy lens)
• glaucoma (pressure of the eye)

Some children with coloboma can have problems with other parts of the body as well. There is a very rare condition where children with coloboma may also have a condition called CHARGE syndrome. This stands for:

• Coloboma
• Heart defect
• Atresia choanae (also known as choanal atresia)
• Restricted growth and development
• Genital abnormality
• Ear abnormality

Children with CHARGE can have poor hearing, learning difficulties, slow growth and problems with their heart.

How are colobomas diagnosed?

You may have noticed that a part of the iris is missing. It may look like a ‘key hole’ or a ‘cat’s eye’. You may also notice, by the way your child acts, that their vision may be impaired. You should ask your GP for an assessment. An eye doctor can then diagnose most colobomas during an examination at the eye clinic.

How can doctors help?

As mentioned previously, children with colobomas are otherwise fine. The eye department will assess the vision and check the health of the eye. If glasses are needed, these will be prescribed. The eye doctor may also request imaging of the eye which will be done during your clinic appointment.

Some children need more monitoring and will be offered a follow up appointment. If the coloboma is not affecting any aspect of vision, your child may be discharged and we would advise that you visit your local optician for a routine check up annually.