How much should a child's eye power increase each year?

When a child’s glasses get stronger at every visit, the question every parent asks is the same: is this normal, or is it rising too fast? It’s the right thing to worry about, because the rate of change matters more than any single number. Here’s the honest way to read it.

First, why it rises at all

Short-sight (myopia) in children rises because the eyeball is growing slightly too long as the child grows. That’s it. It isn’t caused by reading in dim light, watching TV, or “weak eyes,” and it can’t be reversed by food or exercise. The eye lengthens, the number goes up. Our job isn’t to pretend we can shrink it back, it’s to slow how fast it lengthens.

So how much change is “normal”?

There’s no single textbook figure, and any clinic that quotes one precisely is over-simplifying. But as a rough guide that I share with parents:

• A change of around -0.50 dioptre a year is common and fairly typical in a growing, short-sighted child.
• Around -0.75 to -1.00 a year is a faster pace that’s worth watching closely.
• More than -1.00 a year, or jumps that keep getting bigger, is fast progression, and the situation where acting early matters most.

Two honest caveats. Younger children (say 6–9) tend to progress faster than teenagers, so the same number means more in a younger child. And the glasses prescription is a slightly blunt tool, which is why we don’t rely on it alone.

The better measurement: axial length

The glasses number can wobble visit to visit. What we really track is axial length, the actual length of the eyeball, measured on an optical biometer. It’s the most reliable signal of whether the eye is still growing too fast, and it’s how we tell whether treatment is genuinely working, rather than guessing from the spectacle power. We compare each measurement to the last.

Why the rate matters so much

It isn’t about vanity or thicker glasses. A higher final power in adulthood carries a higher lifelong risk of serious eye problems, including retinal detachment and earlier glaucoma. Every dioptre we prevent now lowers that risk for life. That’s the real prize of slowing progression, not removing the glasses, but protecting the eye long term.

When to act

Bring your child in for a proper assessment if:

• Their power has risen two years running, or jumped noticeably in one year.
• They were under 10 when they first needed glasses.
• Short-sight runs in the family (one or both parents).

If progression is confirmed, proven options, low-dose atropine drops, myopia-control lenses, and daily outdoor time, can slow it meaningfully. If it isn’t progressing fast, we’ll tell you that honestly and simply keep watching, rather than start treatment you don’t need.

Worried your child’s power is climbing too fast? See how the children’s myopia clinic measures and slows it, or ask us on WhatsApp. We measure axial length, not just the glasses number.