Astigmatism in children, explained in plain words

Astigmatism is the word on a prescription slip that makes parents look up sharply, mostly because it sounds like something has gone wrong rather than something that simply is. It has not gone wrong. It is one of the most ordinary findings in a children's eye test, and once you see the shape behind the word, the rest of the conversation gets much easier.

I draw the shape on the back of an appointment card most weeks, because it explains in ten seconds what a paragraph cannot. Once a parent has seen it, the glasses, the wearing schedule and the reason we keep checking through the teenage years all follow from the same picture.

What does astigmatism actually mean?

It means the front of the eye, the cornea, or occasionally the lens sitting behind it, is curved unevenly. Picture the surface of a football: curved the same amount in every direction. A normal cornea is close to that shape. In astigmatism, the surface is curved more in one direction than another, closer to the surface of a rugby ball. Because of that uneven curve, light coming into the eye lands at more than one point instead of a single sharp point, so the picture the eye receives is blurred or stretched, at every distance, rather than only far away or only up close.

That last part is what surprises parents most. Short-sightedness blurs distance and long-sightedness blurs near work, so most parents expect astigmatism to behave the same way, favouring one distance. It does not. It affects the whole picture at once, near and far, which is exactly why it is corrected differently: with a cylinder built into the lens rather than the simple round correction used for short or long sight alone.

It is also, very often, not alone. Astigmatism tends to sit alongside short-sightedness or long-sightedness in the same eye rather than replacing them, so a child's prescription may need to correct more than one thing at once. This is found the same way any other refractive error is found in a young child: as part of a dilated eye exam, with drops that relax the eye's own focusing effort so we can measure its true shape, rather than by asking your child how clearly they can see.

Is it because he sits too close to the television?

No, and this is worth saying plainly because it is one of the first questions I get. Nobody knows exactly what causes astigmatism, and there is currently no way to prevent it. Some children are born with it, present from a very young age, and some develop it later in childhood. It is not caused by sitting close to a screen or reading in dim light. It is, however, common in babies and young children, it often runs in families, so it is worth mentioning if you or your partner wore glasses for it as a child, and it usually sits alongside short-sightedness or long-sightedness rather than appearing entirely on its own.

If you have noticed your child sitting unusually close to the television, that habit is still worth mentioning at the same appointment. It is not a cause of astigmatism, but it is very often a sign that a child cannot see the screen comfortably, which is a different, equally useful thing for us to check.

Why does astigmatism matter more in a young child than in an adult?

Because a child rarely tells you it is there. Mild astigmatism can cause no symptoms that a child would recognise as a problem, let alone put into words, and that is exactly why it is found at an eye test rather than reported at home. An adult with new astigmatism usually notices blur or eye strain and does something about it. A child, especially a young one, has no baseline to compare against. If the world has always looked a little stretched, a little smeared at the edges, that is simply what "seeing" means to them, and they will not think to mention it.

Can astigmatism cause a lazy eye?

Yes, and this is the reason astigmatism is worth taking seriously rather than treating as a minor footnote on a prescription. When astigmatism sits in one eye more than the other, the brain quietly leans on the clearer eye and starts to ignore the blurrier one. Vision in that ignored eye can then fail to develop properly, which is the same lazy eye, or amblyopia, that develops for other reasons too. Because the stronger eye is doing all the work, a child in this situation can look and behave completely normally at home, which is exactly why it is missed without a proper test. The earlier uneven astigmatism is found and corrected, the better the chance both eyes develop normally together.

Will it get worse as she grows?

It can change over time, in either direction, and I cannot promise you which way any particular child's astigmatism will go. What I can tell you is that regular eye checks matter more than trying to predict it. There is one specific reason to keep them up through the teenage years: astigmatism that keeps increasing, especially if it increases quickly, is one of the ways a separate condition called keratoconus, where the cornea itself changes shape over time, can first announce itself. That does not mean every child with astigmatism is heading towards keratoconus. It means a changing prescription in a teenager is worth a proper look rather than simply a stronger lens, especially if it comes with more eye rubbing than usual, since the two tend to travel together.

The practical rhythm most families settle into is straightforward: an eye check when astigmatism is first found, a review to confirm the glasses are working as expected, and then checks at whatever interval your child's own doctor sets, more often if something is being watched closely. None of that needs to be memorised. Your child's own eye doctor will set the schedule and tell you plainly if anything changes it.

What do the glasses actually do, and does he wear them all the time?

They correct the uneven curve with a matching uneven curve of their own, built into the lens as a cylinder, so that light from every direction lands back at a single point again rather than being smeared across the retina. It is a well established, straightforward correction, and for most children it is simply glasses, not contact lenses or anything more involved, at least while they are young.

Whether your child needs to wear them every waking hour, or mainly for schoolwork and screens, depends on how much astigmatism is present and whether one eye is more affected than the other, so it is worth asking your child's doctor directly rather than guessing. Where there is any risk to how one eye is developing, consistent wear matters a great deal, in exactly the way it does for any child settling into a first pair of glasses. If you are not sure what an eye test for a young child even involves, particularly one who cannot yet read a chart, this is what actually happens at each age, and it explains why astigmatism can be measured accurately long before your child can describe how anything looks.

None of this needs to feel alarming. Astigmatism is common, it is well understood, and correcting it is one of the more straightforward things we do in a children's eye clinic. It is not something a parent could have prevented and not something a parent needs to manage alone. The only real task is not solving it yourself, but making sure it gets found, worn correctly once it is, and rechecked on schedule as your child grows, so both eyes have every chance to develop exactly as they should.

Common questions

References

1. AAPOS · Refractive Errors in Children · aapos.org
2. NHS · Astigmatism · www.nhs.uk
3. National Eye Institute · Astigmatism · www.nei.nih.gov
4. AAPOS · Astigmatism · aapos.org
5. 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.