Birth features and what they mean

Coloboma: a keyhole shape in the iris, lens or eyelid

A notch in the coloured part of the eye, or a small gap in the eyelid edge, looks alarming in a newborn photo. It comes from one specific, well-understood step in early development, and it is usually calmer than it looks.

by Dr Chan Li Yen · MBBS, MOphth (UM), Fellowship in Paediatric Ophthalmology & Strabismus

Practises at Hospital Kuala Lumpur 11 min read · 1,941 words

Key takeaways

A coloboma is missing tissue where a normal seam in the eye did not fully close in the first weeks of pregnancy, well before most of the pregnancy that follows.
It can affect the iris, lens, choroid, retina, optic nerve, or eyelid, alone or in combination, and which structures are involved matters far more than the fact of having one.
An iris coloboma alone, the visible keyhole pupil, very often has little effect on sight; whether vision is affected depends mainly on whether the retina's central point, the fovea, developed normally.
It can occur in isolation or alongside other features, including CHARGE syndrome and microphthalmia, which is why a baby found to have one is usually examined more broadly.
A coloboma affecting the back of the eye is typically followed with a dilated eye examination roughly every six to twelve months through childhood, because of a recognised long-term risk of retinal detachment.

A notch in the coloured part of the eye, or a small gap in the eyelid edge. It looks alarming in a newborn photo, and it is usually calmer than it looks. The medical name is coloboma, and it comes from a Greek word meaning mutilated or curtailed, which sounds far more dramatic than what most families actually experience once it is properly explained.

This is a different kind of mark from the pigmented patches I have written about elsewhere, such as the blue-grey birthmark around a baby's eye or a birthmark along the eyelid margin. Those are extra pigment sitting where it normally does not. A coloboma is the opposite: a piece of tissue that simply did not finish forming where it usually does.

What actually is a coloboma?

A coloboma is a condition where normal tissue in or around the eye is missing at birth. It happens because, very early in pregnancy, there is a small gap along the bottom of the developing eye that normally closes on its own, before the seventh week. If that gap does not close completely, the child is born with a coloboma at the point where the seam should have joined.

It can affect several different parts of the eye and the eyelid, and doctors name each one separately: an iris coloboma, a lens coloboma, a coloboma of the choroid or retina at the back of the eye, an optic nerve coloboma, or a coloboma of the eyelid itself. A child can have one of these, or more than one together, and which structures are involved matters far more than the fact of having a coloboma at all.

Why does it look like a keyhole?

When a coloboma affects the iris, the coloured ring around the pupil, the missing piece usually sits toward the bottom, giving the pupil a keyhole or teardrop shape rather than its usual round one. That specific, recognisable shape is exactly what it looks like when the same unclosed seam runs through the iris rather than somewhere further back in the eye.

A coloboma of the eyelid looks different again: a small notch or gap right at the lid margin, rather than a shape change in the eye itself. Either version can look startling in a first photograph or under a hospital light, and either version is a structural feature present from birth rather than something that developed afterward or that anything during the pregnancy caused you to do or not do.

It also helps to know how early this happens in development, because it explains why nothing about labour, delivery, or the weeks just before birth is responsible. The seam that fails to close does so in the very first weeks of pregnancy, often before many mothers even know they are pregnant, at a stage where the eye is still forming from a simple cup-shaped structure. A coloboma found on your baby's first newborn examination reflects that early chapter of development, not anything from later in the pregnancy or around the birth itself.

Does a coloboma affect my child's vision?

It depends entirely on which structures are involved, and this is the honest, useful answer rather than a reassuring guess. An iris coloboma alone, the visible keyhole pupil, very often has little effect on sight, because the iris mainly controls how much light enters the eye rather than how the eye focuses or processes an image.

What matters most for vision is whether the back of the eye, and specifically the fovea, the small central point of the retina responsible for sharp detail, developed normally. A coloboma that involves the retina or optic nerve can affect vision more significantly, depending on size and location, which is precisely why an eye specialist needs to examine the back of the eye directly rather than judge the outcome from how the pupil looks from the front. Some children with an eyelid coloboma also need attention to whether the cornea underneath is staying properly moist and protected, since a gap in the lid can affect how well the eye closes.

Does a coloboma mean something else is wrong?

A coloboma is often an isolated finding on its own, but it can also occur alongside other features as part of a wider genetic condition, most notably CHARGE syndrome, and it is often associated with microphthalmia, where the eye itself is smaller than usual. This is exactly why a baby found to have a coloboma is usually examined more broadly, not because something is assumed to be wrong, but because checking is the sensible next step once one part of early eye development did not finish as expected.

A coloboma is also believed to have a genetic basis and can run in families in some cases. That is worth knowing rather than worrying over in isolation; a paediatrician or clinical geneticist, not a single article, is the right place to talk through what it might mean for your own child and family, and many children with an isolated coloboma have no other associated condition at all. A broader newborn check, covering hearing, heart, growth and general development alongside the eye itself, is a normal and sensible part of getting a full picture early, rather than a sign that something further has already been found.

What follow-up does a coloboma actually need?

For a coloboma involving the back of the eye, regular monitoring matters because of a specific, recognised long-term risk: retinal detachment. Eye specialists typically recommend a dilated eye examination, where drops widen the pupil so the retina can be checked properly, roughly every six to twelve months through childhood, or sooner if a doctor has a specific reason to bring the review forward. This interval is set out for posterior colobomas, those affecting the back of the eye; a small, isolated eyelid notch does not need the same monitoring schedule, and your child's own doctor will say plainly which applies.

An eyelid coloboma may also need surgical attention in some children, particularly if the gap is large enough that the eye cannot close fully or the cornea is at risk of drying out, though many small eyelid notches simply need watching rather than early surgery. None of this is decided from how the notch looks in a photograph; it comes from an eye examination that looks carefully at what the coloboma has and has not affected.

What should I actually do if my baby has a keyhole pupil or notched lid?

Have the eye properly examined rather than only photographed. The visible shape, whether it is the pupil or the eyelid edge, tells you that something did not finish closing during early development; it does not by itself tell you whether vision, or anything beyond the eye, is affected. That distinction is exactly what a dilated eye examination, of the kind described in how we test children's eyes, is designed to establish.

From there, most families settle into a routine of periodic review rather than ongoing worry, with the schedule set by what was actually found on examination rather than by how alarming the first photograph looked. A coloboma is a structural feature your child was born with, not a condition that is getting worse simply because you noticed it later than you might have liked, and calm, regular follow-up is the appropriate response for the great majority of children found to have one.

It is worth saying, too, what a coloboma does not mean for daily life. Many children with an isolated iris or small eyelid coloboma go about play, reading and school much like their peers, with the eye examination itself, rather than the appearance of the eye, being the thing that guides whether glasses or any further care at all is the right next step for that particular child.

Don't wait for a check-up if…

Your baby has never had a dilated eye examination after a coloboma was noticed at birth or at a routine check.
An eyelid coloboma is large enough that the eye does not close fully, especially during sleep.
The eye looks red, irritated or unusually dry alongside an eyelid notch.
Your child has a known coloboma and you notice any sudden change in how well they seem to see.
A coloboma is found alongside other features, such as hearing, heart or feeding concerns, that have not yet been discussed with your paediatrician.

Common questions

What is a coloboma?

A coloboma is a condition where normal tissue in or around the eye is missing at birth, because a small gap in the developing eye did not fully close, normally before the seventh week of pregnancy. It can affect the iris, lens, choroid, retina, optic nerve or eyelid.

Why does my baby's pupil look like a keyhole?

When a coloboma affects the iris, the coloured ring around the pupil, the missing piece usually sits toward the bottom, giving the pupil a keyhole or teardrop shape instead of its usual round one. This comes from the same unclosed seam that causes other forms of coloboma, just located in the iris.

Does a coloboma affect vision?

It depends entirely on which structures are involved. An iris coloboma alone very often has little effect on sight, since the iris mainly controls how much light enters the eye. A coloboma affecting the retina or optic nerve can affect vision more significantly, depending on size and location, which is why an eye specialist examines the back of the eye directly.

Did I do something during pregnancy to cause this?

No. The seam that fails to close does so in the very first weeks of pregnancy, often before many mothers know they are pregnant, at a stage where the eye is still forming from a simple cup-shaped structure. It is not linked to anything a mother did or did not do later in the pregnancy.

Is a coloboma genetic, and does it run in families?

It is believed to have a genetic basis and can run in families in some cases. Some children have an isolated coloboma with no other associated condition; others have it alongside features of a wider genetic condition, such as CHARGE syndrome. A paediatrician or clinical geneticist is the right person to discuss what this might mean for your own child.

What is CHARGE syndrome and how does it relate to coloboma?

CHARGE syndrome is a genetic condition in which coloboma is one recognised feature, alongside others such as heart defects and hearing changes, which is why a baby found to have a coloboma is often examined more broadly rather than only at the eye.

What follow-up does a child with a coloboma need?

For a coloboma involving the back of the eye, a dilated eye examination roughly every six to twelve months through childhood is typically recommended, because of a recognised long-term risk of retinal detachment. An isolated small eyelid notch does not need the same schedule; your child's own doctor will confirm which applies.

Does an eyelid coloboma need surgery?

Some children do, particularly if the gap is large enough that the eye cannot close fully or the cornea is at risk of drying out, but many small eyelid notches simply need watching rather than early surgery. This is decided by an eye examination, not by how the notch looks in a photograph.

References

American Academy of Ophthalmology · What Is a Coloboma? · www.aao.org
EyeWiki (American Academy of Ophthalmology) · Coloboma · eyewiki.aao.org
NIH Genetic and Rare Diseases Information Center (GARD) · Iris coloboma · rarediseases.info.nih.gov
NIH Genetic and Rare Diseases Information Center (GARD) · Eyelid coloboma · rarediseases.info.nih.gov

By Dr Chan Li Yen. General information only. It does not replace a consultation. If you are worried about your child's eyes or vision, please see an eye doctor.