Screens & short-sightedness

High myopia: what changes once the number gets high

Short-sighted covers a nine-year-old who needs mild glasses and a nine-year-old whose eyes are stretching fast. The word is the same. What it means for her eyes, once the number is high enough, is not.

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

Practises at Hospital Kuala Lumpur 11 min read · 2,056 words

Key takeaways

High myopia means a prescription of -6.00D or beyond, the International Myopia Institute's consensus threshold, not just a strong-feeling glasses number.
Each additional dioptre of myopia is linked to a meaningfully higher risk of myopic maculopathy, retinal detachment, glaucoma and cataract later in life.
In parts of Asia, 10 to 20% of high-school-aged children already have high myopia, and about one in three people with high myopia go on to develop some visual impairment as adults.
Once myopia reaches the high range, a dilated retinal check is generally added to routine glasses monitoring, at intervals an eye specialist sets for that child.
Treatments that slow further progression, including low-dose atropine and specially designed lenses, are still worth pursuing even after a child's myopia is already high.

Short-sighted covers a lot of ground. A child who needs a mild prescription to see the whiteboard clearly, and a child whose eyes are lengthening fast enough that her retina needs a closer look, both get called short-sighted. The word is the same. What it means for her eyes is not, and once a child's number climbs far enough, a few things genuinely change.

What actually counts as "high" myopia?

A prescription of -6.00 dioptres or beyond, measured as the spherical equivalent with the eye's own focusing effort relaxed by drops. That threshold comes from the International Myopia Institute's consensus definition, adopted so that studies and clinics around the world are talking about the same thing when they say high myopia. Below that number is ordinary short-sightedness, however inconvenient the glasses. At and beyond it, the eye itself has stretched enough, front to back, that the extra length starts to matter for tissue at the back of the eye, not only for how thick the lenses need to be.

How would I know if my child's number has reached that point?

By the number on the prescription itself, not by how the glasses look or how well she manages without them. A child can see reasonably well through a strong prescription and still be in the high range, and a child can complain constantly about blur with a mild one. Power climbing steadily year after year, particularly through the primary school years, is the pattern that eventually crosses -6.00D in some children, more often in children who started young and progress quickly. Onset of high myopia in fast-progressing children has been described clustering around age eleven to thirteen, which is why the school years are the stretch to watch most closely, not because anything sudden happens at that age but because several years of steady progression tend to have accumulated by then. This is worth tracking on the prescription slip itself rather than guessing from behaviour, and it is exactly what a routine eye test is for. What that visit actually involves, at any age, is covered in how we test children's eyes before a child can read.

Why does a longer eye matter more than a blurry one?

Because short-sightedness is not a fault in the lens, it is a change in shape. The eyeball itself has grown a little too long from front to back, so light focuses just in front of the retina instead of directly on it. Glasses or contact lenses correct the blur that causes, but they do nothing to the shape of the eye behind them. A mild degree of extra length rarely causes any trouble beyond needing glasses. A large amount of extra length is a different matter: it stretches and thins the tissue at the back of the eye, including the retina itself, and that stretching is what the rest of this article is actually about. Think of it less like a camera slightly out of focus and more like a balloon being pulled a little too long: the surface it is made of has to stretch to cover the extra length, and stretched tissue behaves differently from tissue at its normal size.

What extra risks come with high myopia later in life?

A meaningfully higher chance of four specific problems, all linked to how stretched the retina and the surrounding tissue have become. One large analysis found that each additional 1.00D of myopia raises the risk of myopic maculopathy, damage to the central retina from long-term stretching, by around 58%, and raises the risk of retinal detachment by around 30%, open-angle glaucoma by around 20%, and posterior subcapsular cataract by around 21%. A separate review of high myopia specifically found that one in three people with high myopia go on to develop some degree of visual impairment as they get older, and that in parts of Asia, 10 to 20% of high-school-aged children already have high myopia. None of this means a child with a high prescription is guaranteed any of these problems. It means the risk is real enough that it changes what gets monitored, which is the next question.

Does a high number mean more frequent eye checks now?

In general, yes: once a child's myopia reaches the high range, guidelines call for a dilated examination of the retina itself, not only a check of the glasses prescription, and for that to happen at intervals a specialist sets based on the individual eye rather than a fixed yearly slot. A dilated check looks specifically for early stretching or thinning at the back of the eye, the kind of change that can exist well before it causes any symptoms a child would mention. Some clinics also measure the eye's actual length, not only its focusing power, because a longer eye is the physical change driving all of this, and tracking it directly can show a trend before the prescription number alone would. This is a decision for the eye doctor following your child, made on her particular numbers and how quickly they have been changing, not a rule to apply from a number alone.

Can treatment still help once the number is already high?

Yes, and this is one of the more reassuring parts of an otherwise sobering topic. The same approaches used to slow ordinary short-sightedness, low-dose atropine drops and specially designed spectacle or contact lenses, are also studied in children whose myopia is already high, with atropine in particular showing a significant slowing effect on further progression at higher concentrations. Slowing the rate of further stretching, even once a child is already in the high range, is worth pursuing precisely because each additional dioptre carries its own added risk, as above. I have set out the honest numbers behind these treatments, including what still is not known, in slowing myopia down: drops, lenses and the honest numbers and, on the drops specifically, in atropine drops for myopia: what the numbers say. Why so many more children are becoming short-sighted in the first place, including the outdoor-time evidence, is covered in why so many children are short-sighted now.

Each additional dioptre is not just a thicker lens. It is a small, measurable rise in risk to the back of the eye.

What should send us in the same day, not wait for the next appointment?

Sudden floaters, sudden flashes of light, or a curtain or shadow moving across part of the vision. These three signs, in a child with a high prescription or a family history of retinal problems, need same-day medical attention rather than a wait for the next scheduled check, because they can be the first sign of a retinal tear or detachment, one of the specific risks named above. They are uncommon in children, and most children with high myopia never experience them. A handful of small floaters that a child has always had, unchanged for months, is not the same thing and does not need the same urgency. What matters is a change: something new, sudden, or spreading. When it does appear, the interval between the sign showing up and the eye being examined is the part that is within a family's control, and it is worth acting on the same day it happens rather than waiting to see if it settles.

So what actually changes once the number gets high?

Not the glasses routine, and not the child's day-to-day life. What changes is the kind of watching that goes on behind the scenes: a dilated look at the retina added to the usual check, a treatment conversation about slowing further progression even at this stage, and a clear, specific list of symptoms that move an appointment from routine to same-day. None of that is a reason for alarm on its own, and a high number today does not mean the risks above are guaranteed to arrive later. It is simply what a high number asks for, once it is named plainly rather than left as one more version of "short-sighted."

See an eye doctor the same day if…

Your child suddenly notices new floaters, especially a shower of them appearing at once.
Your child describes sudden flashes of light, particularly at the edge of vision.
A curtain, shadow or dark area seems to move across part of what they can see.
Any of these appear in a child who already has a high prescription or a family history of retinal detachment.

Common questions

What number counts as high myopia in children?

A spherical equivalent refractive error of -6.00D or beyond, measured with the eye's focusing effort relaxed by drops. This is the International Myopia Institute's consensus definition, used so that clinics and research studies mean the same thing when they use the term. Below that number is ordinary short-sightedness, however strong the glasses feel.

Is high myopia the same as pathological myopia?

No. High myopia describes the number on the prescription. Pathological myopia describes actual structural damage at the back of the eye, such as myopic maculopathy, that can develop in some people with high myopia over time. A child can have a high number for years without ever developing pathological changes, which is exactly why the monitoring described in this article exists.

What extra risks does high myopia actually carry?

A meaningfully higher chance of myopic maculopathy, retinal detachment, open-angle glaucoma and posterior subcapsular cataract, all linked to how much the eye has stretched. One large analysis found each additional 1.00D of myopia raised the risk of these four conditions by roughly 20 to 58%, and a separate review found about one in three people with high myopia develop some visual impairment as they age. None of this is a guarantee for any individual child, but it is why the number is worth tracking properly rather than treated as just a stronger prescription.

Does my child need a dilated eye exam just because the prescription is high?

In general, yes, once myopia reaches the high range, guidelines call for a dilated look at the retina in addition to the usual glasses check, at intervals an eye specialist sets based on that child's own numbers and how fast they have been changing. This is a decision made individually, not a fixed rule that applies the moment a prescription crosses a line.

Can we still slow the myopia down once it is already high?

Yes. Low-dose atropine drops and specially designed spectacle or contact lenses, the same approaches used for ordinary progressing myopia, are also studied in children whose myopia is already high, with atropine at higher concentrations showing a significant slowing effect in that group. Slowing further progression is still worth pursuing at this stage, because each additional dioptre carries its own added risk.

How common is high myopia in children?

It varies a great deal by region. In parts of Asia, reviews report that 10 to 20% of high-school-aged children already have high myopia, reflecting the same rise in childhood short-sightedness seen across the region generally. Rates are lower elsewhere, but the pattern of onset, several years of steady progression through the primary school years, is broadly similar wherever it happens.

What symptoms mean we should not wait for the next appointment?

Sudden new floaters, sudden flashes of light, or a curtain or shadow moving across part of the vision. In a child with a high prescription, these can be the first sign of a retinal tear or detachment and need same-day medical attention. Floaters a child has always had, unchanged for months, are not the same thing and do not need the same urgency.

Does a high prescription mean my child will definitely have eye problems as an adult?

No. A high number raises the statistical risk of certain complications, but most people with high myopia do not go blind, and the monitoring and treatment steps described here exist specifically to catch and slow problems early. A high prescription is a reason for closer, structured watching, not a diagnosis of future disease.

References

International Myopia Institute · Defining and Classifying Myopia: A Proposed Set of Standards for Clinical and Epidemiologic Studies · myopiainstitute.org
Ophthalmology 2021 · Sankaridurg et al, The Risks and Benefits of Myopia Control · pubmed.ncbi.nlm.nih.gov
Ophthalmic & Physiological Optics 2024 · High myopia: Reviews of myopia control strategies and myopia complications · pubmed.ncbi.nlm.nih.gov
Progress in Retinal and Eye Research 2018 · Morgan et al, The epidemics of myopia: Aetiology and prevention · pubmed.ncbi.nlm.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.