What is myopia, and why does it matter for your child

You have just heard the word myopia

Maybe the teacher mentioned your child squinting at the whiteboard from the back row. Maybe they have started sitting closer to the TV, or the B4 School Check letter came home with a referral. Then an optometrist used the words myopia, short-sighted and a number with a minus sign in front of it.

Myopia is the medical name for short-sightedness. A short-sighted child sees a book, a tablet or a face across the table clearly, but the whiteboard, the road signs and the netball at the far end of the court are blurred. Healthify NZ describes it as light rays focusing in front of the retina rather than directly on it.

It is common, it is correctable, and on its own it is not an illness. The reason it gets more attention now than it did when you were at school is what happens to the eye as the prescription climbs.

What is happening inside the eye

The National Eye Institute puts it simply: short-sightedness happens when the eyeball grows too long from front to back. A cornea that is curved more steeply than usual can add to it. Either way, the focused image lands in front of the retina, the light-sensitive layer at the back of the eye, and distance looks soft.

The minus number on a prescription is a measure of how much extra focusing power the lens needs to add. When that number goes up at the next check, it usually means the eye has grown a little longer again. That is why many practices now measure the length of the eye directly, a test called axial length, rather than relying on the prescription alone.

A child's eyes grow with the rest of them, so some change is expected. The question is how fast. Our post on why a child's prescription keeps changing walks through what normal growth looks like and when the pattern is worth a closer look.

Why more children are short-sighted now

The American Academy of Ophthalmology estimates that by 2050 nearly half the people in the world will be short-sighted, and says the condition has been rising for several decades. No single cause explains it. The factors official sources list are a mix of family history and how children spend their days.

KidsHealth NZ lists the main risk factors for a child:

• Having one short-sighted parent raises the chance, and having two raises it further.
• Not spending enough time outdoors. The National Eye Institute notes that children who spend more time outside are less likely to be short-sighted, though researchers are not sure why.
• Long periods of screen use, and long periods of close-up work such as reading and drawing. KidsHealth suggests keeping close work to no more than three hours a day.
• Age. The National Eye Institute says it usually starts between ages 6 and 14 and gets worse until the early twenties, while KidsHealth notes it tends to stabilise for most young people in their early twenties.

Why a higher prescription matters later

This is the part most parents have not heard. The American Academy of Ophthalmology describes myopia as low, moderate or high depending on the strength of the prescription, and says the more severe it is, the higher the risk of retinal detachment. People with severe short-sightedness also carry a higher risk of glaucoma, cataract and other eye disease, and the Academy advises regular retina checks for them. Healthify NZ lists being very short-sighted among the risk factors for retinal detachment.

The reason is physical. A longer eye stretches the retina and the tissues around it. The stretch does not cause problems in childhood, but it stays for life.

Keep this in proportion. Most short-sighted people never have any of these problems, and a moderate prescription in a teenager is not an emergency. The point of slowing myopia in childhood is to finish growing with a lower number than there would otherwise have been, which lowers the lifetime risk. Our post on whether myopia worsens with age covers the usual pattern over time.

What can be done, and what cannot

Ordinary glasses and contact lenses correct the blur. They do not slow the eye's growth, and the American Academy of Ophthalmology is clear that standard single-vision glasses restore distance vision without slowing progression. Nothing reverses myopia that is already there, and KidsHealth NZ notes laser surgery is not recommended for children because their eyes are still developing.

What has changed is that there are now treatments designed to slow progression. The Cochrane living review on myopia control in children, updated in 2025, looked at atropine eye drops, orthokeratology (Ortho-K) overnight lenses, soft multifocal contact lenses, myopia control spectacle lenses and red light therapy. It found the strongest evidence for atropine and Ortho-K over the short term, with higher atropine doses slowing progression most, and said it remains uncertain about the benefit of spectacle and soft lens options. It also noted that most studies ran for two years or less, so longer-term benefit is not yet clear.

Our optometrists fit several of these options, listed on the myopia control page. Not every child needs them. A low prescription that has barely moved in a year, especially in an older teenager, may simply be corrected and watched. If the number is climbing each year, the comparison guide on Ortho-K, soft lenses and glasses for a child is the next thing to read.

When an optometry appointment is the wrong place

Short-sightedness itself is never urgent. Some things that happen to short-sighted eyes are. Healthify NZ says to seek medical care immediately or call 111 if a strong chemical gets in the eye, if something pierces the eye, or if vision is blurred or lost after an injury. For a chemical splash, flush the eye with clean running water for at least 15 minutes first, then get to the nearest hospital emergency department.

Get help the same day, not next week, for a sudden shower of new floaters, flashes of light, a shadow or curtain across part of the vision, or a sudden loss of vision. Healthify lists these as warning signs of retinal detachment, which is more common in very short-sighted eyes. A red, painful eye that cannot tolerate light also needs to be seen urgently. If you are not sure where to go, Healthline on 0800 611 116 is free and open around the clock.

Routine myopia, a changed prescription or a child who has started squinting is exactly what an optometrist is for, and in New Zealand you do not need a referral to book one.

What to do next

If your child has not had a full eye exam, start there. Healthify NZ suggests children and teenagers have an eye examination every one to two years, and KidsHealth NZ recommends a yearly check for children who already wear glasses, because the prescription can change. A children's eye exam with us needs no referral.

If you are not sure whether what you are seeing at home is a vision problem at all, read signs your child needs an eye test first.