What is refraction in an eye exam?

Refraction is the part of an eye exam that measures how your child’s eyes focus light, so the optometrist can determine the best prescription for clear vision. For children with myopia (nearsightedness), accurate refraction is essential—not just for seeing clearly, but also for tracking progression and guiding myopia management.

What happens during a refraction eye exam:

Autorefractor:

Your child may first look into a machine that gives an initial estimate of their prescription. It’s quick and objective—no answers required.

Retinoscopy:

The clinician shines a light into the eye and observes how it reflects. This is especially helpful for younger children who can’t reliably answer “which is clearer?”

Phoropter (the “better 1 or better 2?” part):

Your child looks through different lenses while reading letters. Their responses help fine-tune the prescription.

Cycloplegic refraction (often used in children):

Special eye drops temporarily relax the focusing muscle. This prevents over-focusing and reveals the true level of myopia or farsightedness. It’s very useful when myopia is progressing or when results seem inconsistent.

What the numbers mean on a glasses prescription

Sphere (SPH):

The main strength of the lens. A negative number (e.g., -2.50) indicates myopia.

Cylinder (CYL) and Axis:

These describe and correct astigmatism, a common condition where the eye isn’t perfectly round.

Pupillary distance (PD):

The distance between the centres of the pupils, ensuring lenses are aligned correctly.

Why refraction matters so much for children with myopia

• Clear, comfortable vision: Sharp vision supports learning, sport, safety, and confidence.

• Accurate baseline: Reliable measurements allow your clinician to detect whether myopia is changing—and how quickly.

• Informs myopia management: Precise refraction helps select and adjust evidence-based treatments designed to slow myopia progression.

How often should children have refraction?

At least once a year for school-age children.

Every 6 months if your child already has myopia, especially if glasses prescriptions are changing quickly or if myopia management treatment is underway.

Book sooner if you notice squinting, headaches, sitting close to screens, or a sudden drop in school performance.

Refraction vs. a full eye exam

Refraction determines the best lens power, but it’s only one part of a comprehensive eye exam. Children also need eye health checks (often with dilating drops) to assess the retina, optic nerve, and overall eye structure—important for any child and particularly for those with myopia.

Refraction is the precise measurement that powers clear vision—and it’s a cornerstone of monitoring and managing myopia in children.

For more trusted guidance, evidence‑based options and practical support, read our complete guide on myopia control.