An iris coloboma is a congenital defect in which part of the iris (the coloured ring of tissue around the pupil) fails to develop normally, resulting in a notch or “keyhole”-shaped pupil.
Coloboma broadly refers to missing eye tissue present at birth. When it affects the iris, the pupil may take on an irregular shape. These iris-only defects are among the most visible and common of ocular colobomas. Estimates suggest about 1 in 10,000 births are affected, although some cases may go undetected if mild.
MedBound Times connected with Dr. Bhanu Prakash M, Senior Consultant Cataract, Cornea and Refractive Surgeon at Yashoda Hospitals, Hyderabad to know more about the condition. He explained "iris coloboma most commonly appears on the nasal side of the iris and may be associated with defects in the lens and choroid, referred to as lens coloboma and choroidal coloboma respectively." “It is a congenital, hereditary condition formed during birth,” he explains. “While there is no specific medical treatment, surgical correction through pupilloplasty is safe and effective in restoring the normal appearance of the pupil.”
Other names used include “keyhole pupil” or “cat-eye pupil” because of the appearance. Symptoms vary depending on how much iris tissue is missing and whether other parts of the eye are affected. In many cases of iris coloboma the primary noticeable sign is the pupil shape anomaly and some light sensitivity. If the coloboma extends into the retina or optic nerve, visual problems such as reduced acuity or field loss may occur.
In an Instagram reaction reel posted on his profile, Dr. Julian Prosia, a board-certified optometrist and dry eye specialist, explains the major types and symptoms of keyhole pupil (iris coloboma). He was reacting to another viral reel featuring financial journalist Andrew Ross Sorkin with the condition in an interview featured by "60 minutes", which gained widespread attention due to the distinctive appearance of their eye. He was talking about AI (Artificial intelligence) boom when netizens started to notice his eye appearance rather than what he was saying.
An iris coloboma is a type of ocular coloboma. Colobomas can affect different parts of the eye: the iris, lens, retina, choroid, optic nerve or eyelid. The underlying cause is a developmental defect during early gestation: specifically, the embryonic fissure (optic fissure) fails to close properly, often in the inferonasal quadrant of the eye, leaving a gap in ocular tissue. Genetic mutations, inherited conditions, or environmental factors (for example maternal exposures) may contribute, although many individual cases have no identifiable cause.
For an isolated iris coloboma (only the iris is affected), many individuals may have normal or near-normal vision and live without major impairment; the primary challenge may be light sensitivity or cosmetic concerns. However, if the coloboma involves deeper structures (retina, optic nerve or choroid), this can lead to more serious outcomes: reduced visual acuity, retinal detachment, glaucoma or cataracts over time. Lifelong monitoring by an eye specialist is recommended to detect and manage these potential complications early.
Diagnosis of an iris coloboma is generally made by an ophthalmologist through a detailed eye examination, often at birth or in early childhood.
Dr. Prakash adds that iris coloboma can be clinically diagnosed using a slit-lamp examination, a simple outpatient procedure that can even be documented photographically. “Treatment options include colored cosmetic contact lenses to mask the defect or a surgical procedure known as four-throw pupilloplasty, where the iris defect is corrected using fine sutures (10-0 Prolene). The procedure is straightforward and typically takes 15 to 30 minutes,” he notes.
Iris coloboma is present at birth and results from incomplete closure of the optic fissure during eye development.
It may appear as a “keyhole” shaped pupil and often causes minimal vision issues if only the iris is involved.
The condition may be more serious when other ocular structures are affected, requiring ongoing monitoring for complications such as glaucoma or retinal detachment.
While no treatment restores the missing tissue, many people with iris coloboma lead normal lives with appropriate monitoring and supportive care.
References
American Academy of Ophthalmology. “What Is a Coloboma?” Disease Review. Accessed October 30, 2025. https://www.aao.org/education/disease-review/what-is-coloboma.
ScienceDirect Topics. “Iris Coloboma.” Accessed October 30, 2025. https://www.sciencedirect.com/topics/medicine-and-dentistry/iris-coloboma.
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