Squint & lazy eye

One of my baby's eyelids droops lower than the other, what does that mean?

A droopy upper lid since birth is not about how your baby looks. It is a lid muscle that did not finish developing, and the reason we watch it closely is vision, not appearance.

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

Practises at Hospital Kuala Lumpur 11 min read · 2,048 words

Key takeaways

A droopy upper eyelid present from birth, congenital ptosis, is usually caused by a lid muscle that did not develop fully before birth.
It matters for two reasons that are both about vision: the lid can press on the eye and blur it, and rarely it can cover the pupil enough to stop sight developing.
A baby who tilts the chin up or works the eyebrows to see is telling you the lid is in the way.
Surgery is timed by whether vision is affected, not by an age on the calendar.
Most children with a mildly droopy lid are simply monitored, with surgery reserved for those where vision or the risk to it is real.

Almost every week a parent brings me a photograph on their phone before we have even sat down, one eye open a little less than the other, and asks whether it is something to worry about. Usually it has been there since birth, and usually the eyelid itself is not the worry. What that lid is doing to the vision underneath it is.

Most of these babies are entirely well otherwise, feeding, sleeping and growing exactly as expected. The lid is often the only thing anyone has noticed, sometimes at the hospital in the first days, sometimes much later in a family photo where one eye simply looks smaller. Both routes bring parents to the same question, and the answer starts the same way for all of them: a proper look, not a guess.

What is congenital ptosis?

Congenital ptosis is a droopy upper eyelid present from birth, caused by a lid-lifting muscle that did not develop fully before your baby was born. The muscle is called the levator, and in these children it is simply weaker than it should be, on one side or occasionally both. It is not an infection, not an injury, and nothing you did or missed during pregnancy.

The muscle itself is what is affected, not the eye behind it. Some babies have a lid that sits a millimetre or two lower than the other and stays that way through childhood. Others have a lid low enough to sit over the pupil for part or all of the day. The amount of droop is what decides how closely we watch, and eventually whether we treat it at all.

It can affect one eye or both, and the two sides do not need to match for the diagnosis to be the same condition. A baby with only one droopy lid is not more or less likely to have congenital ptosis than a baby with two, and treating each eye is judged separately, on its own measurements, rather than by comparing it to its neighbour.

Why does a droopy eyelid matter for vision, not just looks?

It matters because of what the lid can do to the eye underneath, not because of how the eye looks in photographs. There are two separate routes, and I explain both at the first visit because they are treated differently.

The first is pressure. A lid that rests on the front of the eye can gently change its shape over time, producing astigmatism, an eye that is no longer perfectly round and so focuses light unevenly. Left uncorrected, that blur in early childhood is exactly the kind of thing that can turn into a lazy eye, because a young visual system that never receives a sharp image in one eye can simply stop trying to use it properly.

The second route is rarer and more direct. If the lid covers the pupil completely, light cannot reach the retina at all, and sight in that eye does not develop the way it should. This is uncommon, but it is the reason a lid that closes off the pupil, even only sometimes, is not something to leave until the next routine visit.

A chin lifted up or eyebrows working hard is your child telling you the lid is in the way.

Why does my toddler tilt his head back or raise his eyebrows to look at me?

Because that is often how a child compensates for a lid that sits too low. Tipping the chin up moves the whole face so the eyes can look out from under a drooping lid rather than through it, and working the forehead muscles lifts the eyebrow, and with it, a little of the lid. Both are the body finding a workaround, and both are worth telling us about.

Parents sometimes describe this as a habit or a quirk before they connect it to the eyelid at all. It rarely is just a habit. A child who has learned to tilt or raise the brows to see is showing you, without being able to say so, that the droop is genuinely getting between them and a clear view of the world. That is useful information, not something to correct by asking them to stop.

How do we check whether a droopy lid is affecting vision?

By measuring how much lid function remains and by testing the eye itself, not by looking at a photograph. We measure how far the lid lifts, how far it covers the pupil in different positions of gaze, and whether the droop changes when your child looks up or down. We also check for any astigmatism the lid may already be causing, and we assess each eye for early signs of a lazy eye developing. Much of this, like how we test children's eyes before they can read, needs nothing from your child except their cooperation for a few minutes, which a toy or a torch usually buys us. The same visit is a natural point to fold in the wider checks covered in a baby's first eye checks, since a droopy lid is rarely the only thing worth confirming while your child is already sitting still for us.

Because astigmatism and a lazy eye can both hide behind an apparently mild droop, we do not judge the lid on appearance alone. A lid that looks only slightly low can still be causing enough pressure on the eye to matter, while a lid that looks quite low can sometimes be causing very little. The measurements tell us which situation we are in, and how often to bring your child back.

When is surgery needed for congenital ptosis?

Surgery is needed when the droop is affecting vision in a way glasses or watching cannot fix on their own, and the timing is decided by that, not by an age on the calendar. If the lid sits clear of the pupil and no astigmatism or lazy eye is developing, we can often simply monitor a child through the years that matter most for vision, reviewing regularly rather than operating early.

Where surgery is needed, there are two main approaches, chosen by how much the levator muscle still works. If there is some useful function left, we shorten that muscle so it lifts the lid further. If there is effectively none, we sling the lid to the forehead muscle instead, so raising the eyebrows does the lifting the levator cannot. Neither operation restores a lid that is identical to its neighbour, and no honest surgeon promises that. The aim is a lid that clears the pupil and protects the vision behind it.

Even after surgery is decided on, there is rarely a need to rush it into the newborn months. Most operations are planned once a child is old enough for a safe general anaesthetic and stable enough for the surgeon to measure lid function accurately, which usually means the toddler or preschool years unless the pupil is being blocked now. Waiting for the right window is not neglect. It is how the timing gets decided properly, case by case.

What if it is an adult asking about a droopy eyelid, not a baby?

A droopy lid in an adult is a different problem with a different cause, most often the lid tissue stretching or thinning with age rather than a muscle that failed to develop before birth, and it belongs with a surgeon who treats adult eyelids. If you are reading this about your own eye rather than your child's, what a droopy lid means in an adult and what the operation involves is written by Dr Catherine Chow, a consultant oculoplastic surgeon whose practice is exactly this. I see children's eyes, and this is genuinely her territory, not mine. Her wider set of adult eyelid conditions is where to look if the ptosis question is only part of what brought you to her site.

What should I actually do if I have noticed a droopy eyelid?

Book an assessment rather than wait to see if it changes on its own. A first look costs you little time and settles a question that is otherwise very hard to judge from home, and if all is well, you leave with peace of mind rather than a diagnosis. If the lid ever covers the pupil, if your child is tipping the chin or raising the brows constantly, or if you notice a squint alongside the droop, that visit should not wait for a routine slot. For everything else, we simply keep an eye on it together, at the pace your child's eyes actually need.

Don't wait for a check-up if…

The droopy lid covers all or most of the pupil, even sometimes.
Your baby tips the chin up or raises the eyebrows constantly to see under the lid.
The droop is new, or one lid is closing further as time goes on rather than staying the same.
You notice a squint or a drifting eye alongside the droop.
The lid droop came with an unusual head tilt or a family history of ptosis or lazy eye.

Common questions

One of my baby's eyelids is lower than the other, is that normal?

It is common enough that we see it every week, and it is not something to ignore either. In most children it is congenital ptosis, a lid muscle that did not develop fully before birth, and it is not dangerous in itself. What matters is whether it affects vision, so it is worth a proper look rather than a guess from a photo.

Will she grow out of a droopy eyelid?

Sometimes the droop stays exactly the same through childhood and is dealt with on its own timeline, but it does not reliably fix itself the way some baby features do. We watch it rather than wait for it to resolve, because the risk is to vision, and a change for the worse is more useful to catch early than to discover late.

Does a droopy eyelid cause lazy eye?

It can, by two separate routes. A lid pressing on the front of the eye can change its shape and cause astigmatism, which blurs vision if left uncorrected, and that blur can become a lazy eye. Rarely, a lid that covers the pupil blocks light so completely that the eye never learns to see properly. Neither route is automatic, which is exactly why we check.

Why does my toddler tilt his head back to look at me?

A raised chin is often a child finding a way to see under a droopy lid rather than through it. Working the eyebrows to lift the lid is the same idea. Both are worth mentioning at your next visit, because they usually mean the lid is genuinely getting in the way of sight, not just sitting a little low.

At what age is droopy eyelid surgery done?

There is no fixed age. The decision is driven by whether vision is affected or seriously at risk, and by glasses or other treatment not being enough to fix that on their own. A lid that is not troubling vision can often be left and simply reviewed, sometimes well into childhood.

How is congenital ptosis actually treated if surgery is needed?

There are two main operations, and which one we use depends on how much the lifting muscle still works. Where there is some function, we shorten that muscle. Where there is effectively none, we sling the lid to the brow muscle instead so the forehead can lift it. Your surgeon chooses based on what your child's lid tests show.

Can a droopy eyelid be a sign of something else?

Usually it is an isolated finding, but a droopy lid can occasionally appear alongside other issues, which is one reason a full assessment is worth having rather than judging the lid on its own. If the droop is new rather than present from birth, or comes with anything unusual in eye movement, that is a different picture and should be checked sooner rather than later.

References

AAPOS · Ptosis · aapos.org
American Academy of Ophthalmology · Ptosis in children · www.aao.org
NHS · Eyelid problems · www.nhs.uk
AAPOS · Amblyopia (lazy eye) · aapos.org

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.