Keratoconus in teenagers, and the eye rubbing link

Key takeaways

In keratoconus the cornea, the clear dome at the front of the eye, thins and bulges into a cone, so the picture arrives distorted rather than simply blurred.
It affects about one person in every two thousand, is more common in people of Asian background, and usually shows itself in puberty or the late teens.
The teenage clue is a prescription that will not settle: astigmatism that keeps increasing, worse night vision, streaks around lights and ghosted images.
Eye rubbing is strongly and repeatedly linked with keratoconus, which makes it worth stopping, though no study has shown that rubbing caused it in a particular child.
Asthma, eczema and allergies are all associated with keratoconus, and treating the itch properly is what actually stops the rubbing.

The sentence that starts most of these appointments is not about eyes at all. It is about the optical shop. We have changed her glasses three times in two years and they are still not right. Parents say it apologetically, as though repeated trips to the optician were an admin failure rather than clinical information.

Most of the time it is not a clue to anything. Short sight in a growing teenager genuinely does move, and that is ordinary. But there is one condition where a prescription that refuses to settle is the first thing a family notices, and it announces itself at exactly this age. It is called keratoconus, and one part of it is something a family can act on.

What is keratoconus, in plain words?

The cornea, the clear dome at the very front of the eye, becomes too thin and bulges forward into a cone shape. Light coming through a cone arrives distorted rather than simply out of focus. That is the whole condition, and it is why stronger lenses stop being the answer.

It happens in about one person in every two thousand, and it is more common in people of Asian background, which is worth knowing in a Malaysian family. It usually affects both eyes, though rarely to the same degree, so one eye can be much worse while the other reads the chart happily. Most people find out they have it during puberty or in their late teens. After it starts, it tends to get worse over ten to twenty years and then stops. In children it is often more aggressive than in adults, which is why I would rather see a teenager early than once the cornea has already changed a great deal.

The front of the eye from the side. Left, a normal cornea curves as an even dome. Right, a cornea thinned by keratoconus bulges into a cone, so the picture arrives distorted rather than merely blurred.

Why does the prescription keep changing?

Because the shape being measured keeps changing. Glasses correct the curve of the eye as it was on the day of the test. If that curve is slowly steepening, every new pair is accurate for a while, then quietly is not, and the family ends up back at the counter.

The pattern I look for is not simply a number that has gone up. It is astigmatism that keeps increasing, visit after visit, together with the things that go with a distorted cornea. Vision that is worse at night. Streaks or starbursts around headlights and lamps. Ghosting, where a single object looks doubled or shadowed even with one eye closed. Light that has started to bother them. And the giveaway that parents describe best: glasses that were meant to fix it and only half did. The NHS says the same thing in one line on its astigmatism page: astigmatism can be linked to keratoconus, so regular eye tests matter. If your child has recently been through a first prescription, none of this means the glasses were wrong. It means the eye is worth mapping as well as measuring.

Does rubbing really cause it, or is that a scare story?

Neither, quite. Rubbing is linked to keratoconus strongly enough, and often enough, that every eye doctor asks about it. It has never been shown to cause the condition in any particular child. Both halves are true.

The study I would put in front of a parent compared 118 people in Poland who had keratoconus with 73 who did not. Eye rubbing came out with odds around seven times higher among those with keratoconus, alongside male sex and dusty environments. The authors argue that repeated mechanical trauma to the front of the eye is what does the damage, and physically that makes sense: a thin, weak cornea pressed hard with a knuckle, day after day, for years.

What that kind of study cannot do is tell you which came first. People whose eyes are uncomfortable rub them, and keratoconus makes eyes uncomfortable. So the honest position, and the one I take in clinic, is that rubbing is a repeated and serious association worth stopping, not a proven cause in your child. The American Academy of Ophthalmology puts the practical version plainly: with keratoconus, avoid rubbing your eyes, because it can damage thin corneal tissue and make symptoms worse. If you are here because your child rubs their eyes constantly, that article is the one that sorts out why they are doing it in the first place.

Stopping the rubbing is worth doing. Blaming yourself for not having stopped it earlier is not.

He has eczema and asthma, does that matter for his eyes?

Yes, and in two separate ways. Asthma, eczema and allergies are all listed among the conditions associated with keratoconus, along with Down syndrome, Marfan's syndrome and Leber's congenital amaurosis. That is the first link, and not one a family can change.

The second link is the one that matters day to day, because it is fixable. Allergic eyes itch. A teenager whose eyes itch every single evening will rub every single evening, and telling them to stop is close to useless while the itch is still there. So in a child with a steepening cornea I get much more interested in treating the allergy properly. The target is the itch, not the willpower. If you recognise the grey shadows under the eyes that come with year-round allergy, that pattern has its own explanation, and it points at the same underlying problem. Antihistamine drops, a cool compress before bed and dealing with the dust in the bedroom will do more to stop a hand reaching an eye than any amount of reminding.

How is it diagnosed and what happens next?

With a map. Alongside the ordinary examination we use corneal topography, which builds a three dimensional picture of the corneal surface and shows thinning and steepening long before it is obvious any other way. It is painless: your child looks at a target for a few seconds.

Treatment splits in two, and it helps to keep the halves separate. One half is about seeing well now. Mild keratoconus is often managed with glasses or soft contact lenses, and most people end up in rigid lenses, because a hard lens sits on the cone and gives the eye a smooth front surface to look through. The other half is about stopping the cornea getting worse, a different aim altogether. The treatment used for that is collagen cross linking, in which riboflavin drops and ultraviolet light strengthen the cornea. It may need a specialist and, in a young child, a general anaesthetic. I am naming it as a category, because what suits a particular cornea is a conversation with the doctor holding the scans.

The trial worth knowing about randomised sixty young people aged ten to sixteen with progressive keratoconus. Over eighteen months, the cornea got worse in seven per cent of the treated eyes and in forty three per cent of the eyes given standard care alone. Sixty children over eighteen months in the United Kingdom is a small and short study, not a final word, and it points the same way as everything else here: reach a cornea before it has changed, not after. A minority of people with keratoconus eventually need a corneal transplant, a figure quoted for everyone with the condition rather than for children. One thing is not a judgement call at all: nobody with keratoconus should have LASIK, at any age, because it makes the eye worse.

When should I stop waiting and book?

When the prescription has changed twice in a year and the glasses still do not feel right, book an eye examination rather than another refraction. That is the whole message, and it does not need a dramatic symptom behind it. Ask specifically whether the cornea has been mapped.

Two other prompts. If a sibling, parent or grandparent has keratoconus, say so, because it runs in families and it changes how closely I want to watch a teenager who is also a determined rubber. And if your child ever has a sudden drop in vision in one eye with pain and redness, that needs to be seen quickly rather than at the next appointment: a thinned cornea can develop a blister, and that is painful rather than something to sit on over a weekend.

The least dramatic part of this is also the truest. Most teenagers whose glasses keep changing do not have keratoconus. They are simply short sighted and growing, which is happening to more children than it used to. Finding out which takes one appointment and a scan that lasts a few seconds. If it is the ordinary answer, you have lost an afternoon. If it is not, you have found it at the stage where finding it counts for the most.

Ask for an eye examination, not another refraction, if…

The glasses prescription has changed twice or more in a year and the vision is still not right.
Astigmatism keeps increasing at each visit, or your teenager reports ghosted images, streaks around lights, or vision that is much worse at night.
A parent, brother or sister has keratoconus, especially if your child also rubs their eyes hard.
Your child rubs constantly because of an itch that has never been properly treated.
There is a sudden drop in vision in one eye with pain and redness. That one needs to be seen quickly rather than at the next appointment.

Common questions

Her glasses prescription keeps changing, is something wrong?

Usually not. Short sight in a growing teenager genuinely moves, and a change every year or so is ordinary. What is worth a closer look is astigmatism that keeps increasing visit after visit while the glasses never quite work, because that is one of the ways keratoconus announces itself. Ask for an eye examination with corneal topography rather than simply another refraction.

What is keratoconus?

It is a condition in which the cornea, the clear dome at the very front of the eye, becomes too thin and bulges forward into a cone shape. Light passing through a cone arrives distorted rather than out of focus, which is why stronger glasses stop helping. It happens in about one person in every two thousand and is more common in people of Asian background.

He rubs his eyes constantly, can that damage them?

Hard, habitual rubbing over years is linked with thinning and bulging of the cornea, so it is worth stopping. In one case control study the odds of keratoconus were around seven times higher among people who rubbed. Rather than telling your child off, find out why they are rubbing. An untreated itch is the commonest reason, and it is treatable.

Does rubbing actually cause it, or is that a scare story?

Neither. The link is real and repeated, and it has never been shown that rubbing caused keratoconus in any particular child. Studies that compare people with and without the condition cannot tell you which came first, since a cone shaped cornea is itself uncomfortable. The honest reading is that rubbing is worth stopping, and that nobody should be blamed for a cornea that has changed shape.

He has eczema and allergies, does that matter for his eyes?

Yes, in two ways. Asthma, eczema and allergies are all associated with keratoconus, which is not something a family can change. They are also the reason a child rubs, and that part is very fixable. Treating an allergic eye properly does more to stop the rubbing than any amount of reminding, so it is worth raising at the appointment.

What is cross linking, and does it fix the vision?

Collagen cross linking uses riboflavin drops and ultraviolet light to strengthen the cornea. Its aim is to stop the cornea getting worse, not to improve the sight, and glasses or contact lenses still do the seeing. In a trial of sixty young people aged ten to sixteen, the cornea worsened in seven per cent of treated eyes over eighteen months against forty three per cent of eyes given standard care alone. Whether it suits a particular cornea is a discussion with the doctor holding the scans.

Will he need contact lenses, or a transplant?

Mild keratoconus is often managed with glasses or soft contact lenses, and most people eventually need rigid lenses to see clearly, because a hard lens gives the eye a smooth front surface to look through. A minority of people with keratoconus need a corneal transplant, and that figure is quoted for everyone with the condition rather than for children.

Can she have laser surgery when she is older?

Not LASIK. Anyone with keratoconus should avoid it, because removing tissue from a cornea that is already thin makes the eye worse. This is one of the few absolute rules in eye care, and it is a reason to have the diagnosis on record now rather than to discover it at a laser clinic in ten years.

References

AAPOS · Keratoconus · aapos.org
American Academy of Ophthalmology · What is keratoconus? · www.aao.org
Larkin DFP et al · Effect of corneal cross-linking versus standard care on keratoconus progression in young patients: the KERALINK randomized controlled trial, Ophthalmology 2021 · pubmed.ncbi.nlm.nih.gov
Jaskiewicz K et al · Non-allergic eye rubbing is a major behavioral risk factor for keratoconus, PLoS One 2023 · pmc.ncbi.nlm.nih.gov
NHS · Astigmatism · www.nhs.uk

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.