What it means and why
Axial length is a physical front-to-back eye measurement in millimetres. Refraction describes optical focus in dioptres. They are related, but the curvature and power of the cornea and crystalline lens also contribute to the refractive result.
For follow-up, the change over time and measurement consistency are important. A single length without age, previous measurements and the rest of the examination cannot describe a person’s whole risk profile.
A worked example
Teaching scenario: two records have similar SPH but different axial lengths. That is possible because the eyes’ other optical components differ. For one child, compare repeat measurements using an appropriate clinical protocol rather than translating every millimetre into a fixed prescription change.
What it does not tell you
There is no universal conversion from axial length to a complete glasses prescription. An axial measurement cannot replace refraction, retinal assessment or clinical judgement.
THINK IT THROUGHCan the same prescription occur with different axial lengths?
Yes. Eye length and the powers of the focusing structures jointly determine refraction.
Sources & reading notes
Page updated:
- International Myopia Institute · Defining and classifying myopia ↗ Research guidance
Check the report’s definitions and intended population before applying a conclusion.
- International Myopia Institute · Clinical management guidelines ↗ Research guidance
Check the report’s definitions and intended population before applying a conclusion.