This page is about coloboma, currently available treatments and appropriate medical management.
It covers the different types of coloboma, the parts of the eye that can be affected, diagnosis and related eye conditions.
You’ll also find links to more detailed information on a number of the topics included here.
Sections on this page
- What is coloboma?
- What parts of the eye can coloboma affect?
- How is coloboma diagnosed?
- Types of coloboma
- How is coloboma treated?
- Can coloboma cause other eye health problems?
What is coloboma?
The C in CHARGE stands for coloboma. Coloboma comes from a Greek word meaning “not fully formed”.
A coloboma means that the tissue of one or more parts of an unborn baby’s eye does not fully develop during pregnancy.
This normally happens in the lower part of the eye and can be small or large.
A coloboma occurs in about 1 in 10,000 births, by the eighth week of pregnancy. It is then present from birth and into adulthood.
Coloboma can affect one eye (unilateral) or both eyes (bilateral), and can affect different parts of the eye.
It may be hard to tell what effect coloboma will have on your child’s sight until they are older and can describe more accurately how well they can see.
What parts of the eye can coloboma affect?
Coloboma can affect the following parts of the eye:
How is coloboma diagnosed?
Coloboma is normally diagnosed when a baby is born or in a very young child.
Iris coloboma can usually be seen as a keyhole-shaped pupil.
Sometimes, children with iris coloboma also have different coloured eyes, which is called “iris heterochromia”.
If you notice these features in your child, your GP or optometrist (someone trained to recognise eye imperfections and conditions) should normally refer them to an ophthalmologist (eye specialist doctor).
The ophthalmologist will examine your child’s eyes in detail for coloboma in any other part of their eye.
They may also carry out other tests, including:
- Measuring your child’s visual field – what they can see to the sides, above and below when looking straight ahead. The accuracy of this test depends on your child being able to respond.
- Looking at the different structures of their eyes using a slit lamp, a special type of microscope.
- Optical coherence tomography (OCT), which provides an image of the different layers of the retina without touching the eye.
- Computerised tomography (CT) or magnetic resonance imaging (MRI) scans the structures of the eye.
A young baby may be given a general anaesthetic so that their eyes can be examined without causing distress.
If your child has a chorioretinal coloboma, it might look as if they have a white pupil instead of the red reflex normally seen in pictures taken using flash photography.
A white pupil – leukocoria – can be a sign of other serious eye conditions.
If you notice that your child has a white pupil at any time, it’s important that they are examined by an optometrist or ophthalmologist urgently.
Types of coloboma
There are five types of coloboma.
The iris is the tissue that gives the eyes colour. With iris coloboma:
- Your child’s pupil may look oval if they have partial iris coloboma.
- Their pupil will look more keyhole-shaped, if more of the lower iris is missing.
- Children and adults will probably have fairly good vision.
- There’s a likelihood of light sensitivity – photophobia – in bright conditions because too much light enters the eye.
Tinted glasses, sun hats or sun blinds in cars can help to relieve light sensitivity. Speak to your optometrist for further advice about this.
The lens is a transparent structure behind the pupil of the eye.
Lens zonules are fibres that hold the lens of the eye in place, just behind the iris.
If a section of lens zonules is defective or missing, this is referred to as lens coloboma, even though none of the lens tissue itself is missing.
With lens coloboma:
- The lens is not held as strongly all the way round.
- This alters its shape, causing a notch or dent in the lens.
- This notch or dent in turn affects vision.
- There may also be some degree of cataract in the affected eye, which means the lens is cloudy instead of clear.
The retina and the choroid are at the back of your eye. The retina is a membrane (a thin layer) lining the inner surface of the back of the eyeball. The choroid is a layer of tissue behind the retina. It contains blood vessels that keep the retina healthy.
When the retina and the choroid are affected by coloboma, this is known as a chorioretinal coloboma.
With chorioretinal coloboma:
- There may be no obvious symptoms.
- However, the more retinal tissue that is missing, the more your child’s vision is likely to be affected, usually in the upper visual field.
- If the chorioretinal coloboma is large, or your child also has optic disc coloboma, they are likely to have poor central vision, making reading, writing and watching TV more difficult.
Optic disc coloboma
The optic disc is the point where major cells of the retina gather and leave the eye to form the optic nerve, which carries visual information to the brain.
When coloboma affects the optic nerve at this point, this is known as optic disc coloboma.
Although optic disc coloboma is present from birth, diagnosis may come later because it is inside the eye and can’t be seen by simple inspection.
With optic disc coloboma:
- How much vision is affected depends on how severe the coloboma is.
- Your child may have other features such as
- microphthalmia (a small eye) with or without a cyst.
- microcornea (a small cornea – the clear, protective outer layer).
- coloboma affecting other parts of the eye.
- There is a risk of retinal detachment.
If both your child’s eyes are affected by optic disc coloboma, they may also have nystagmus, meaning their eyes move constantly and uncontrollably.
Eyelid coloboma is not as common as other types of coloboma.
Although gaps in the eyelids are still known as coloboma, they don’t have the same cause that leads to coloboma in other parts of the eye.
How can coloboma be treated?
If your child has coloboma, they will receive specialist care at hospital in their early years to monitor the effect of the coloboma and their eye health.
How often this happens will depend on their needs.
Can coloboma be treated with glasses and contact lens?
No, none of the types of coloboma listed above can be corrected with glasses or contact lenses.
But, it’s important for your child to have any other focusing problems, such as being short-sighted or long-sighted, corrected to allow their sight to develop as fully as possible.
Therefore, it’s important for your child to have regular eye examinations as often as their optometrist advises.
Also, although many children and adults with iris coloboma don’t need any treatment, they often have a special contact lens fitted to cover the keyhole-shaped pupil and make it look round.
This also reduces light sensitivity.
Iris coloboma surgery
With iris coloboma, surgery is sometimes an option. The gap in the iris is sewn together to correct the pupil shape and reduce light sensitivity.
You can discuss this option with your child’s ophthalmologist.
Regular eye examinations
For other types of coloboma inside the eye, there are presently no treatments.
But, regular eye examinations with an optometrist are essential to check eye health.
The optometrist will tell you how often they are needed.
If your child experiences any new symptoms, or you have any concerns, arrange an eye examination straight away.
It is important for children to have regular low-vision assessments because their vision needs change as they grow up.
An ophthalmologist, optometrist or GP can refer your child to their local low-vision clinic, which is often located in the hospital eye department.
Eye clinic liaison officers
Your eye clinic may also have an eye clinic liaison officer (ECLO), who can provide you with further practical and emotional support about your child’s eye condition.
Can coloboma cause other eye health problems?
Sometimes, coloboma can increase the risk of other eye conditions, including:
Amblyopia, known as “lazy eye”, can be treated using an eye patch.
Having a cataract means the eye’s lens is cloudy, causing blurred or misty vision, colours appearing dull and glare in your vision, particularly when driving at night.
Some people with coloboma will develop a cataract at an earlier age than people without coloboma.
If vision cannot be improved with glasses, adults with cataracts can have surgery to remove the cloudy lens and replace it with a clear artificial one.
This procedure can be more complex for a child with coloboma and cataracts.
Your child’s ophthalmologist will carry out an in-depth assessment before discussing ways to manage the condition.
Choroidal neovascularisation (new blood vessels)
Some people with chorioretinal and optic disc coloboma can develop new blood vessels in the choroid behind the retina.
These new vessels are weak and leak and bleed easily, damaging vision.
Treatment is available in the form of anti-VEGF injections into the white of the eye, which reduce new blood vessel growth and leakage.
Glaucoma is an eye condition where the optic nerve is damaged by the pressure of fluid inside the eye.
People with coloboma may be at greater risk of glaucoma.
Ptosis, or drooping upper eyelid, can be treated with surgery to reattach the muscle or tendon to the eyelid.
With chorioretinal coloboma, there is a greater risk of a retinal detachment – the retina pulling away from the back of the eye.
Symptoms include floaters and flashes of light in your vision. Some people also experience a curtain effect coming down, up or across their vision.
Surgery is possible but needs to be done urgently to prevent further sight loss in that eye.
Strabismus is known as “turned” or “crossed” eyes. This can be corrected by surgery to either loosen or tighten the eye muscles, as needed.
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This content was last reviewed in April 2022. We’ll review it again next year.