A coloboma is an area of missing tissue in your eye. Colobomas are present in a person’s eye when they’re born. They can affect one or both eyes. The most common colobomas develop in your iris and cause your pupil to have a keyhole or cat-eye shape.


A coloboma in the iris of an eye.
Colobomas most commonly affect the iris of the eye. They give the pupil a keyhole shape.

What is a coloboma?

A coloboma is an area of missing tissue in your eye. Colobomas are present in a person’s eye when they’re born. They can affect one or both eyes.

The most recognizable and common colobomas affect your iris (the colored part of your eye) and cause your pupil (the dark center of your eye) to have a keyhole shape. But there are many types of colobomas, most of which you can’t see externally (on the outside).

Some colobomas cause no symptoms, but others can have serious impacts on your child’s vision. What symptoms they’ll have depends on where in their eye the coloboma developed and which kind of tissue they’re missing.

Your healthcare provider might be able to diagnose a coloboma when your baby is born.


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Who gets colobomas?

Anyone can be born with a coloboma.

They’re a type of genetic disorder, which means they’re passed from parents to their children. You might see coloboma referred to as a congenital condition.

However, even if one parent (or both) has a coloboma, that doesn’t mean your child will definitely develop one.

How common are colobomas?

Colobomas affect around 1 out of every 10,000 babies born each year.

Because not all colobomas cause noticeable symptoms, that number might be higher. Some people have an undiagnosed coloboma and never have symptoms or complications.


How does a coloboma affect my child’s body?

How much a coloboma affects your child depends on where in their eye it’s located. Colobomas can develop in one eye (unilateral coloboma) or both eyes (bilateral coloboma). Bilateral colobomas might affect different parts of your eyes.

Some colobomas won’t impact your child’s vision. Others cause total blindness in the affected eye. If your child has a coloboma on their retina, macula or optic nerve, they might have some vision, but it might be impaired.

You might not notice a coloboma affecting your child’s vision right away, especially while they’re very young.

People with colobomas might be more likely to have other issues with their eyes later in life, including:

Colobomas can develop in almost any part of your child’s eye, including their:

Coloboma of the iris

Colobomas of the iris are the most common type of coloboma. The iris is the colored part of your eye.

Babies born with a coloboma of the iris are sometimes referred to as having a congenital iris coloboma. Congenital is the medical term that means something is present at a person’s birth. Just like other types of colobomas, iris colobomas can be unilateral (only affecting one iris) or bilateral (affecting both irises). People with iris colobomas can also have other colobomas on their retina or optic nerve, too.

Colobomas of the iris are diagnosed and treated just like other types of colobomas. Some people with iris colobomas wear special contact lenses to help cover their pupils more completely. Surgery to change the appearance of an iris coloboma is an option, but not everyone is a good candidate for it. Talk to your provider or eye care specialist about which treatments will work for your child and when they should receive them.

What does an iris coloboma look like?

A coloboma of the iris can give your child’s pupil a keyhole or cat-eye shape. The shape depends on where in their iris it is and how much tissue is missing.

It might look like their pupil is “leaking” into the colored part of their eye. Nothing is in danger of falling out or moving around in your child’s eye. Both the iris and pupil are solid layers of tissue. The missing piece of your child’s iris is simply revealing more of the pupil under it that would usually be covered.

Does an iris coloboma affect vision?

A coloboma of the iris can affect your child’s vision.

Muscles in your iris control your pupil — the small black opening that lets light into your eye. Babies born with an iris coloboma are missing tissue in their iris. This can make it harder for their iris to control how wide (dilated) or narrow (contracted) their pupil is.

Depending on how big the coloboma is, it can cause symptoms that affect your child’s vision, including:

  • Light sensitivity (photophobia).
  • Blurry vision.
  • Double vision (diplopia).
  • “Ghost images,” blurry copies of an image you’re looking at or parts of an image that remain after you move your eyes.


Symptoms and Causes

What are the symptoms of a coloboma?

If your child has symptoms from their coloboma, they can include:

  • Light sensitivity.
  • A keyhole or cat-eye-shaped pupil.
  • Low vision, blindness or partial vision loss.
  • Nystagmus.

A coloboma might only affect a portion of your child’s field of vision (the full range of how much they can see). Colobomas can cause:

  • Reduced peripheral vision.
  • Difficulty with depth perception.
  • A larger than usual blind spot.

What causes colobomas?

Experts think a genetic disorder that affects a fetus’s eye while its developing during pregnancy causes colobomas.

Around two months before a baby is born, what’s known as the optic fissure comes together to form their eyes. When the fissure doesn’t completely close, it causes colobomas in one or both of your baby’s eyes.

Genes are made of DNA (deoxyribonucleic acid), which contain instructions for cell functioning and the characteristics that make you unique. Studies have shown links between certain genes in parents and the likelihood that their children will be born with a coloboma, but there isn’t enough evidence to say for sure which exact genes are responsible.

Certain external factors — like drinking alcohol during pregnancy — can increase the odds that your baby develops a coloboma.

Diagnosis and Tests

How is a coloboma diagnosed?

Your provider or an ophthalmologist will diagnose a coloboma during your child’s eye exam. They’ll examine your child’s eye and look inside it to identify any missing tissue. Every person with a visible coloboma (one you can see on the outside) should have a dilated eye exam to check for other colobomas inside their eye.

Management and Treatment

How are colobomas treated?

There isn’t a treatment to replace the missing tissue in your child’s eyes.

However, there are treatments that might improve their vision, including:

  • Wearing corrective lenses (glasses or contacts).
  • Wearing an eye patch to prevent a lazy eye (amblyopia).
  • Low vision aids (if their vision can’t be improved with corrective lenses).

Some people with iris colobomas can have surgery to change the appearance of their affected eye.


How can I prevent a coloboma?

You can’t prevent genetic conditions like colobomas from developing during your pregnancy.

Colobomas — and other genetic conditions — are linked to certain environmental factors (things that happen to or around a person who is pregnant), including:

  • Drinking alcohol.
  • Smoking or using tobacco products.
  • Using recreational drugs.

Talk to your provider about what you should avoid eating, drinking or doing while you’re pregnant.

Outlook / Prognosis

What can I expect if my child has a coloboma?

How much a coloboma affects your child’s life depends on where it is in their eye. Many people with colobomas never have any symptoms and can live their whole lives without any complications. Other people’s vision is affected from birth.

Even if a coloboma impairs your child’s sight, it isn’t fatal and can’t spread.

Very rarely, a coloboma is sign of what’s known as CHARGE syndrome — a genetic syndrome that can be life-threatening. Talk to your provider or ophthalmologist about your baby’s risk and what you and your child should expect as they grow and develop.

Living With

When should I see my healthcare provider?

See your healthcare provider as soon as you notice any changes in your child’s eyes or vision.

Go to the emergency room if your child has any of the following symptoms:

What questions should I ask my doctor?

  • What type of coloboma does my child have?
  • How will this affect their vision?
  • What treatments are available?
  • Do they have a higher risk for other issues in their eyes?

A note from Cleveland Clinic

A coloboma is a permanently missing piece of your child’s eye. Even if it never causes symptoms or vision issues, it will be with them their whole life. How much a coloboma impacts your child’s vision depends on where in their eye it develops. Talk to your provider about any changes or new symptoms in your child’s eyes as soon as they appear.

Medically Reviewed

Last reviewed on 12/27/2022.

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