Why Measuring Eye Growth Matters in Childhood Myopia

January 14, 2026

If you only track glasses prescriptions, you are missing part of the story

When a child's nearsightedness gets worse, most parents expect one thing to change: the glasses prescription.

What is less obvious is why that prescription is changing.

In most children, myopia progresses because the eye itself is growing longer. That physical change is called axial elongation, and it is one of the key drivers of myopia progression ¹.

That is why modern myopia care looks beyond prescriptions alone.

At Spadina Optometry, we use axial length measurement as part of how we monitor eye growth, guide treatment decisions, and explain risk in a way parents can understand.

What parents usually ask first: What is axial length?

Axial length is the front to back length of the eye, measured in millimetres.

A longer eye focuses light in front of the retina
That is what causes myopia (nearsightedness)
Faster or excessive eye growth is linked to higher eye health risks later in life ¹, ²

International myopia guidelines recognize axial length as an important outcome measure in myopia management, alongside the prescription and not instead of it ¹.

Prescriptions describe how clearly a child sees.
Axial length reflects how the eye itself is changing.

Why prescriptions alone do not tell the full story

Two children can have the same glasses prescription but very different patterns of eye growth.

That is because:

Prescriptions change in steps such as 0.25 or 0.50 diopters
Eye growth happens gradually
A child's eyes may be elongating before the prescription clearly shifts

Measuring axial length helps clinicians:

Detect progression earlier
Compare growth against age expected norms
Evaluate whether a myopia management strategy is slowing eye growth ¹

Clinical consensus shows that axial length is often a more sensitive indicator of progression than prescription changes alone.

That is why we do not rely on a single number.

How axial length is measured and what it is like for kids

Axial length measurement is:

Non contact
Quick, usually seconds
Comfortable and easy for children

There are no drops, no air puffs, and no discomfort.

For parents, the value is not the test itself. It is what the measurements show over time.

How we use axial length at Spadina Optometry

At Spadina Optometry, axial length measurement helps us move from reactive care to planned monitoring.

We use it to:

Establish a baseline early in myopia management
Track eye growth trends over time
Reassess strategies if growth is faster than expected
Explain progress clearly using simple comparisons and visuals

Axial length numbers do not make decisions on their own.
They support clinical judgment.

Monitoring helps us avoid both unnecessary intervention and missed progression.

How often is axial length checked?

Most children in myopia management are reviewed every 3 to 6 months, depending on age, rate of progression, treatment type, and individual risk factors ¹.

A colleague at another Canadian clinic puts it simply:

Axial length helps us see whether eye growth is slowing, not just whether the prescription looks stable.

Insight Eye Care, Waterloo

Some children need closer monitoring during growth spurts. Others remain stable for longer periods. Follow up schedules are individualized.

Why eye growth matters beyond today's vision

Slowing myopia progression is not only about seeing clearly this year.

Long term studies link higher degrees of axial elongation with increased lifetime risks of:

Retinal detachment
Myopic macular degeneration
Glaucoma
Other retinal complications ², ³

This does not mean every nearsighted child will develop these conditions.

It does mean that understanding and monitoring eye growth early matters.

What changes when axial length is part of the plan?

When eye growth is tracked, decisions become clearer.

For example:

A stable prescription with ongoing eye growth may still need adjustment
Slower eye growth helps confirm that a strategy is working
Parents can see progress in objective terms, not just wait and see

As one collaborating clinic notes:

Seeing axial length trends helps parents understand why follow ups matter, even when vision seems unchanged.

Mission Eye Care, Calgary

A shared approach across Canadian eye care clinics

Axial length based monitoring is increasingly used by pediatric focused optometry clinics across Canada as part of evidence based myopia management.

Clinics using this approach include:

Toronto: Spadina Optometry
Winnipeg: Waverley Eye Care
Ottawa: Merivale Vision Care
Calgary: Mission Eye Care
Waterloo Region: Insight Eye Care
Vancouver, BC: Eye Lab

Clinics listed use axial length as part of myopia monitoring. Inclusion is informational and reflects shared clinical practices, not endorsements.

Thinking about myopia management for your child?

If your child's prescription is changing, or you are wondering whether it might be, understanding how their eyes are growing can be an important first step.

You can: