Coloboma: What It Is, Why It Happens, and How It's Treated
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer
A coloboma is an area of missing tissue in the eye that is present at birth, affecting one or both eyes. In the iris, it gives the pupil a keyhole or cat-eye shape. A gene change stops the optic fissure from fully closing. The tissue cannot be replaced, but glasses, patches, low vision aids or surgery can help. [1] [2] [3]
What the research says
Coloboma is uncommon, and it often comes with other conditions. In a population-based study of 33 children, the incidence was 2.4 per 100,000 people under 19, and the prevalence was 1 in 2,077 live births. 67% had one affected eye, 58% had other eye disorders (including amblyopia in 33% and strabismus in 30%), and 67% had a non-eye disorder, including CHARGE syndrome in 12%. (Nakamura et al., Archives of Ophthalmology, 2011) [3]
Where the coloboma sits strongly affects vision. In a study of children with optic disc coloboma (8.9 per 100,000 children), best-corrected visual acuity was 0.82 when the coloboma involved only the optic disc, versus 0.15 when the macula was also involved. (Skriapa Manta et al., Acta Ophthalmologica, 2019) [4]
Eye complications can follow, so lifelong eye care matters. A clinical review explains that typical coloboma results from defective closure of the embryonic fissure, can be sporadic, inherited or chromosomal, and that vision is most affected when the optic disc or fovea is involved or when retinal detachment, cataract or amblyopia develops. It also notes that preventive laser treatment of the retina may lower retinal detachment risk. (Lingam et al., Eye, 2021) [5]
What Is a Coloboma?
A coloboma is an area of missing tissue in your eye. It is present when a person is born and can affect one or both eyes. [1][2]
The most recognizable and common colobomas affect the iris, the colored part of the eye, and give the pupil (the dark center of the eye) a keyhole shape. But there are many types, and most cannot be seen from the outside. [1]
Some colobomas cause no symptoms, while others seriously affect vision. What a child experiences depends on where in the eye the coloboma is and which kind of tissue is missing. A healthcare provider may be able to diagnose a coloboma at birth. [1]
Who Gets Colobomas?
Anyone can be born with a coloboma. It is a type of genetic disorder, and doctors call it a congenital condition, meaning it is present at birth. [1] Even if one or both parents have a coloboma, the child will not necessarily have one. [1]
How Common Are Colobomas?
Cleveland Clinic reports that colobomas affect around 1 in every 10,000 babies born each year, and the true number may be higher because some people have an undiagnosed coloboma and never have symptoms. [1] Study estimates differ: the Minnesota population-based study above found a prevalence of 1 in 2,077 live births. [3]
How Does a Coloboma Affect the Body?
How much a coloboma affects a child depends on its location. It can develop in one eye (unilateral) or both eyes (bilateral), and bilateral colobomas can affect different parts of each eye. [1]
Some colobomas do not change vision at all. Others cause total blindness in the affected eye. With a coloboma of the retina, macula or optic nerve, a child may have some vision, but it may be reduced. Vision problems may not be obvious in very young children. [1]
People with colobomas may also be more likely to develop other eye problems later in life, including cataracts (clouding of the lens), glaucoma (eye damage from high fluid pressure) and retinal detachment (the retina pulling away from the back of the eye). [1][2] You can read more about glaucoma.
A coloboma can develop in almost any part of the eye:
Iris: the colored part of the eye. This is the most common location.
Retina: the light-sensing layer at the back of the eye.
Optic nerve: the nerve that carries signals from the eye to the brain.
Macula: the small area of the retina responsible for sharp central vision.
Ciliary body: the structure that helps the eye focus and produces eye fluid.
Eyelid: the protective covering of the eye.
What is a coloboma of the iris?
Iris colobomas are the most common type. Babies born with one are said to have a congenital iris coloboma. It can affect one iris or both, and people with an iris coloboma can also have colobomas of the retina or optic nerve. [1]
Iris colobomas are diagnosed and treated like other colobomas. Some people wear special contact lenses to cover the pupil more completely, and surgery can change the look of the iris, although not everyone is a good candidate. [1][2]
What Does an Iris Coloboma Look Like?
An iris coloboma can give the pupil a keyhole or cat-eye shape, depending on where the missing tissue is and how much is missing. [1] It can look as if the pupil is "leaking" into the colored part of the eye, but nothing is falling out or moving around. The iris and pupil are solid layers of tissue, and the missing piece of iris simply shows more of the pupil that would normally be covered. [1]
Does an Iris Coloboma Affect Vision?
It can. Muscles in the iris control how wide or narrow the pupil is, and missing iris tissue can make that control harder. [1] Depending on the size of the coloboma, this can cause:
light sensitivity (photophobia)
blurry vision
double vision (diplopia)
"ghost images," which are blurry copies of what you are looking at, or parts of an image that linger after you move your eyes
What Are the Symptoms of a Coloboma?
Light sensitivity: discomfort in bright light.
Keyhole or cat-eye pupil: a pupil that looks notched.
Low vision or vision loss: partial or total loss of vision, or blindness, in the affected eye.
Nystagmus: uncontrolled, repetitive eye movements.
A coloboma may affect only part of the field of vision, which is the full range of what a person can see. It can reduce peripheral (side) vision, make depth perception harder, and create a larger-than-usual blind spot. [1]
What Causes Colobomas?
Experts believe a genetic change affecting the eye as it develops during pregnancy causes colobomas. Early in pregnancy, around the fifth to seventh week, a gap in the developing eye called the optic fissure closes. When it does not close completely, a coloboma forms in one or both eyes. [1][2]
Genes are made of DNA, which holds the instructions for how cells work. Studies link certain genes in parents to the chance that a child is born with a coloboma, but there is not yet enough evidence to say exactly which genes are responsible. [1] Outside factors such as drinking alcohol during pregnancy may also raise the odds. [1][2]
How Is a Coloboma Diagnosed?
A healthcare provider or an ophthalmologist (an eye doctor) diagnoses a coloboma during an eye exam by looking at and inside the eye to find any missing tissue. [1] A visible coloboma can sometimes be spotted at birth, and anyone with a visible coloboma should have a dilated eye exam to check for other colobomas inside the eye. [1][2]
How Are Colobomas Treated?
Colobomas cannot be fixed by replacing the missing tissue, because no treatment exists that can do so. Treatments can still help a child make the most of their vision: [1][2]
Corrective lenses (glasses or contacts): may improve vision.
Special contact lenses: can help cover the pupil more completely in iris colobomas.
Eye patch: used to prevent a lazy eye (amblyopia). Read more about amblyopia (lazy eye).
Low vision aids: help when glasses or contacts cannot improve vision enough.
Iris surgery: can change the look of an iris coloboma, but not everyone is a good candidate.
Related conditions such as cataracts or glaucoma are treated if they develop. [2]
What can you expect if your child has a coloboma?
How much a coloboma affects daily life depends on where it is. Many people never have symptoms and live their whole lives without complications, while others have reduced vision from birth. Even when a coloboma affects sight, it is not fatal and it cannot spread. [1]
Sometimes, a coloboma is a sign of CHARGE syndrome, a genetic syndrome that can be life-threatening. [1] In the Minnesota study, 12% of children with coloboma had CHARGE syndrome. [3] Ask your provider or ophthalmologist about your baby's risk and what to expect as your child grows.
Can a Coloboma Be Prevented?
You cannot prevent a genetic condition like coloboma from developing during pregnancy. [1] Colobomas and other genetic conditions are linked to certain environmental factors, including drinking alcohol, smoking or using tobacco products, and using recreational drugs during pregnancy, so talk to your provider about what to avoid while pregnant. [1][2]
When Should You See a Healthcare Provider?
See your healthcare provider as soon as you notice any change in your child's eyes or vision. [1]
Emergency alert: Go to the emergency room if your child has a sudden loss of vision, severe eye pain, or new flashes or floaters in the eyes. [1]
Questions to Ask Your Doctor
What type of coloboma does my child have?
How will it affect their vision?
What treatments are available?
Do they have a higher risk for other eye problems?
Conclusion
A coloboma is an area of missing eye tissue present at birth. It can affect one or both eyes, and the most common type affects the iris and gives the pupil a keyhole shape. Some colobomas cause no symptoms, while others cause light sensitivity, reduced vision or vision loss, so the location of the missing tissue matters most. The tissue cannot be replaced, but glasses or contacts, eye patches, low vision aids and sometimes iris surgery can help, and regular eye exams catch complications early. [1][2][4][5] See your provider promptly for any change in your child's eyes or vision, and go to the emergency room for sudden vision loss, severe eye pain, or new flashes or floaters.
Frequently Asked Questions
What is a coloboma?
A coloboma is an area of missing tissue in the eye that is present at birth. It can affect one or both eyes.
Is a coloboma present at birth?
Yes. Colobomas are congenital, meaning they are present at birth.
If a parent has a coloboma, will the child have one?
Not necessarily. Even if one or both parents have a coloboma, the child will not definitely develop one.
How common is coloboma?
Cleveland Clinic estimates about 1 in 10,000 babies. A Minnesota population-based study found about 1 in 2,077 live births, so estimates vary.
What does an iris coloboma look like?
An iris coloboma can give the pupil a keyhole or cat-eye shape. Nothing is leaking or falling out of the eye; the missing iris tissue just shows more of the pupil.
Does a coloboma affect vision?
It depends on where it is. Some colobomas do not change vision, while others cause blindness in the affected eye. Involvement of the macula or optic nerve can reduce vision.
What causes a coloboma?
Experts believe a genetic change affects eye development in pregnancy so the optic fissure does not fully close. Drinking alcohol during pregnancy may raise the odds.
How is a coloboma diagnosed?
An eye doctor examines the eye. Anyone with a visible coloboma should have a dilated eye exam to look for other colobomas inside the eye.
Can a coloboma be cured?
No treatment replaces the missing tissue, but glasses, contact lenses, eye patches, low vision aids and sometimes iris surgery can help vision or appearance.
Is a coloboma dangerous?
A coloboma is not fatal and cannot spread, although it can affect vision. Sometimes it is a sign of CHARGE syndrome, so ask your doctor about your child's risk.
What eye problems can develop later with a coloboma?
People with colobomas may be more likely to develop cataracts, glaucoma and retinal detachment later in life.
When should I go to the emergency room?
Go right away for sudden vision loss, severe eye pain, or new flashes or floaters in the eyes.
Related Reading on Rinnit.com
References
Cleveland Clinic Staff. Coloboma: Types, Causes & Associated Conditions. Cleveland Clinic. December 27, 2022. https://my.clevelandclinic.org/health/diseases/22682-coloboma
National Eye Institute. Coloboma. NEI, National Institutes of Health. December 6, 2024. https://www.nei.nih.gov/eye-health-information/eye-conditions-and-diseases/coloboma
Nakamura KM, Diehl NN, Mohney BG. Incidence, ocular findings, and systemic associations of ocular coloboma: a population-based study. Arch Ophthalmol. 2011;129(1):69-74. PMID 21220631. https://doi.org/10.1001/archophthalmol.2010.320
Skriapa Manta A, Olsson M, Ek U, Wickström R, Teär Fahnehjelm K. Optic disc coloboma in children – prevalence, clinical characteristics and associated morbidity. Acta Ophthalmol. 2019;97(5):478-485. PMID 30549247. https://doi.org/10.1111/aos.13999
Lingam G, Sen AC, Lingam V, Bhende M, Padhi TR, Xinyi S. Ocular coloboma-a comprehensive review for the clinician. Eye (Lond). 2021;35(8):2086-2109. PMID 33746210. https://doi.org/10.1038/s41433-021-01501-5
Medical disclaimer
This article is for general information only and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health provider with any questions about a medical condition. Never disregard professional medical advice or delay seeking it because of something you read here. Only a healthcare provider or ophthalmologist can determine the type, location and appropriate care for a coloboma through a proper eye exam. Go to the emergency room immediately for sudden vision loss, severe eye pain, or new flashes or floaters.
Comments