Medically reviewed by Dr. Niranjana Bejan Singh. Written to established clinical-education standards (AAO/Mayo/NHS/NEI) and adapted for this hospital. Not a substitute for professional medical advice.
Refraction is the test used to determine whether a person has a refractive error — nearsightedness (myopia), farsightedness (hyperopia), astigmatism, or age-related difficulty focusing up close (presbyopia) — and to work out the exact lens power needed to correct it. The result is written as an eyeglass (or contact lens) prescription. It is one of the most common and fundamental parts of any eye examination.
Who typically needs this
- Anyone with blurred vision at distance, near, or both, whether or not they have been prescribed glasses before.
- Children and adults due for a routine vision check, including school-age children who may have undiagnosed refractive errors affecting learning.
- People noticing gradual difficulty reading small print, especially after around age 40, a common sign of presbyopia.
- People whose current glasses no longer feel sharp, or who experience eye strain, headaches, or squinting with near or distance tasks.
What to expect
- The doctor or optometrist may start with an automated instrument to get an initial estimate of the refractive error.
- Using a device called a phoropter (or trial lenses), the examiner shows a series of lens options while the patient reads a chart, refining the prescription with feedback.
- Both eyes are tested separately, and near vision may be tested separately from distance vision, particularly in patients over 40.
- The final result is recorded as a prescription showing sphere (short/long-sightedness power), cylinder and axis (astigmatism correction) for each eye, and an addition power for reading if needed.
Recovery
- There is no recovery involved — refraction is a non-invasive test with no after-effects.
- If dilating drops were used as part of a broader eye exam, temporary blurred near vision and light sensitivity may occur, unrelated to the refraction test itself.
- New glasses may feel slightly different for the first few days as the eyes adjust, especially with a significant change in prescription.
- A repeat refraction is reasonable if new glasses do not feel right after a short adjustment period.
Risks to know about
- Refraction itself carries no physical risk — it involves only lenses and a reading chart.
- An inaccurate or rushed refraction can occasionally result in a prescription that does not feel comfortable, which is why patient feedback during the test matters.
- Refraction alone does not check the internal health of the eye, so it should generally be paired with a broader eye health examination.
- Prescriptions can change over time, so an old refraction should not be assumed accurate indefinitely.
Frequently asked questions
How often should my glasses prescription be checked?
Generally every one to two years for adults, more often for children or anyone with an eye condition, or sooner if vision changes noticeably.
Why do I need to try so many lens combinations?
Comparing lens pairs helps the examiner precisely pinpoint the power that gives the sharpest, most comfortable vision for each eye.
Does a refraction check for eye diseases like glaucoma?
No — refraction only measures focusing power for glasses; eye disease screening requires a separate comprehensive eye health examination.
Can children have their vision refracted accurately?
Yes, refraction can be performed on children, sometimes using drops to relax focusing muscles for a more accurate reading, especially in younger children.
Ready to see us?
Call the appointment desk, or book online — we will confirm your time by phone.
Sources consulted: AAO — How to Read an Eyeglasses Prescription, NEI — Refractive Errors . General medical information — not a substitute for professional diagnosis. Medically reviewed by Dr. Niranjana Bejan Singh.
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