Coloboma of the iris
Keyhole pupil; Cat eye syndrome; Iris defectColoboma of the iris is a hole or defect of the iris of the eye. Most colobomas are present since birth (congenital).
Iris
The iris is the colored part of the eye. It is located between the cornea and lens. The round, central opening of the iris is called the pupil. Ve...
Considerations
Coloboma of the iris can look like a second pupil or a black notch at the edge of the pupil. This gives the pupil an irregular shape. It can also appear as a split in the iris from the pupil to the edge of the iris.
A small coloboma (especially if it is not attached to the pupil) may allow a second image to focus on the back of the eye. This may cause:
- Blurred vision
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Decreased visual acuity
Decreased visual acuity
There are many types of eye problems and vision disturbances, such as: Halos Blurred vision (the loss of sharpness of vision and the inability to see...
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If it is congenital, the defect may include the retina, choroid, or optic nerve.
Retina
The retina is the light-sensitive layer of tissue at the back of the eyeball. Images that come through the eye's lens are focused on the retina. Th...
Choroid
The choroid is the layer of blood vessels and connective tissue between the white of the eye and retina (at the back of the eye). It is part of the ...
Most colobomas are diagnosed at birth or shortly afterward.
Causes
Most cases of coloboma have no known cause and are not related to other abnormalities. Some are due to a specific genetic defect. A small number of people with coloboma have other inherited developmental problems.
When to Contact a Medical Professional
Contact your health care provider if:
- You notice that your child has what appears to be a hole in the iris or an unusual-shaped pupil.
- Your child's vision becomes blurred or decreased.
In addition to your child, you may also need to see an eye specialist (ophthalmologist).
What to Expect at Your Office Visit
Your provider will take a medical history and do an exam.
Since the problem is most often diagnosed in infants, knowing about the family history is very important.
The provider will do a detailed eye exam that includes looking into the back of the eye while the eye is dilated. An MRI of the brain, eyes, and connecting nerves may be done if other problems are suspected.
MRI
A head MRI (magnetic resonance imaging) is an imaging test that uses powerful magnets and radio waves to create pictures of the brain and surrounding...
References
Brodsky MC, Houghton O. Congenital optic disc anomalies. In: Yanoff M, Duker JS, eds. Ophthalmology. 6th ed. Philadelphia, PA: Elsevier; 2023:chap 9.5.
Freund KB, Sarraf D, Mieler WF, Yannuzzi LA. Congenital and developmental anomalies of the optic nerve. In: Freund KB, Sarraf D, Mieler WF, Yannuzzi LA, eds. The Retinal Atlas. 2nd ed. Philadelphia, PA: Elsevier; 2017:chap 15.
National Eye Institute (NIH) website. Coloboma. www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/coloboma. Updated November 15, 2023. Accessed December 6, 2023.
Olitsky SE, Marsh JD. Abnormalities of pupil and iris. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 640.
Porter D. American Academy of Ophthalmology website. What is a coloboma? www.aao.org/eye-health/diseases/what-is-coloboma. Accessed December 6, 2023.
Selzer EB, Blain D, Hufnagel RB, Lupo PJ, Mitchell LE, Brooks BP. Review of evidence for environmental causes of uveal coloboma. Surv Ophthalmol. 2022;67(4):1031-1047. PMID: 34979194 pubmed.ncbi.nlm.nih.gov/34979194/.
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Eye - illustration
The eye is the organ of sight, a nearly spherical hollow globe filled with fluids (humors). The outer layer (sclera, or white of the eye, and cornea) is fibrous and protective. The middle layer (choroid, ciliary body and the iris) is vascular. The innermost layer (retina) is sensory nerve tissue that is light sensitive. The fluids in the eye are divided by the lens into the vitreous humor (behind the lens) and the aqueous humor (in front of the lens). The lens itself is flexible and suspended by ligaments which allow it to change shape to focus light on the retina, which is composed of sensory neurons.
Eye
illustration
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Coloboma of the iris - illustration
A coloboma is a defect in the iris of the eye. It can appear as a black notch of varying depth at the edge of the pupil, giving the pupil an irregular shape. Coloboma is a congenital iris defect. Sometimes eye surgery or trauma can cause a defect that looks like a coloboma.
Coloboma of the iris
illustration
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Eye - illustration
The eye is the organ of sight, a nearly spherical hollow globe filled with fluids (humors). The outer layer (sclera, or white of the eye, and cornea) is fibrous and protective. The middle layer (choroid, ciliary body and the iris) is vascular. The innermost layer (retina) is sensory nerve tissue that is light sensitive. The fluids in the eye are divided by the lens into the vitreous humor (behind the lens) and the aqueous humor (in front of the lens). The lens itself is flexible and suspended by ligaments which allow it to change shape to focus light on the retina, which is composed of sensory neurons.
Eye
illustration
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Coloboma of the iris - illustration
A coloboma is a defect in the iris of the eye. It can appear as a black notch of varying depth at the edge of the pupil, giving the pupil an irregular shape. Coloboma is a congenital iris defect. Sometimes eye surgery or trauma can cause a defect that looks like a coloboma.
Coloboma of the iris
illustration
Review Date: 11/8/2023
Reviewed By: Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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