What is a refraction test?
It is the measurement that produces your glasses prescription: the lens power that gives the clearest vision for distance. It is a vision measurement rather than a health check, which is why a refraction alone cannot detect glaucoma, retinal disease or a corneal problem.
- Subject
- Surgery journey
- Topic
- Eye tests & scans
- Kind of question
- What is…
- Last reviewed
- 22 September 2026
In more detail
This is the distinction worth holding on to when comparing appointments. An optician’s sight test normally includes a refraction and a look at the health of the eye; a surgical assessment adds measurements of the cornea and retina that a refraction cannot provide.
What this answer depends on
- Whether the measurement was taken with the eye relaxed
- Whether the test included a dilated examination
- Whether it was repeated on a second occasion
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Where this answer sits
It is one of 483 answers in the vision and eye health knowledge base, filed under The surgery journey in Eye tests & scans . The subject page carries the answers either side of it, and the hub is searchable.
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This information is for educational purposes and does not replace an examination by a qualified eye-care professional.
General answers cannot tell you what is happening in your own eyes. Only an examination by a qualified ophthalmologist can do that.
Sources & further reading
We prefer primary sources. Where a claim comes from a manufacturer, a single study or a regulator, it is labelled as such below.
- EyeSmart: eye health information for the public
Patient-facing material from the largest ophthalmology professional body, covering conditions, tests and treatments outside refractive surgery.
Used for Cross-checking patient-facing explanations of non-refractive eye conditions; Describing what tests such as dilation and OCT involve.
Link checked 23 September 2026