Glasses power can change for reasons unrelated to growth, such as accommodation and measurement method. Axial length is a more direct and repeatable measure of how fast the eye is growing, which is why most myopia management guidance recommends it alongside refraction.
Take it consistently
- Use the same optical biometer for every visit if you can. Different devices differ by small but real amounts.
- Take several readings and keep the average or the device's own composite value, and repeat if the readings disagree.
- Record whether cycloplegia was used. Cycloplegic drops can change readings slightly, so measure under the same conditions each time.
- Record the date, device and both eyes. Keep the printout or the image so values can be checked later.
Set a baseline before treatment
Ideally you have two readings before treatment starts, a few months apart, to see this child's own growth rate. If the child is already on treatment, record when it began and treat that visit as the baseline.
How often
Most clinics measure every 6 months, and every 3 to 4 months in the first year or when growth is fast. Look at the trend over two or more visits rather than reacting to one reading.
Interpreting the change
- Compare growth with what is typical for the child's age. Growth is fastest in younger children and slows with age.
- Even children without myopia still show some axial growth through the school years, so the goal is slow growth, not zero.
- Compare the child with population growth charts for the child's age and background where available.
- Look at refraction, axial length and keratometry together. A rise in axial length with a flatter cornea can hide a change in glasses power.
When to act
If growth stays well above what you expected after treatment has been used correctly, first check adherence, lens fit and wearing time. Then consider changing or combining treatment. Our treatment planner shows one way to frame partial and poor response for a child's age.
This article is general information and not medical advice. For your child, see an eye doctor.
References
- Wolffsohn JS, Flitcroft DI, Gifford KL, et al. IMI: Myopia Control Reports Overview and Introduction. Invest Ophthalmol Vis Sci 2019;60:M1-M19.
- Gifford KL, Richdale K, Kang P, et al. IMI: Clinical Management Guidelines Report. Invest Ophthalmol Vis Sci 2019;60:M184-M203.
- Tideman JWL, Polling JR, Vingerling JR, et al. Axial length growth and the risk of developing myopia in European children. Acta Ophthalmol 2018;96:301-309.