Refraction is an assessment used to determine how light is focused by the eye and what optical correction may provide clearer vision. It is commonly used when determining a prescription for glasses or contact lenses.
What is refraction?
Refraction assesses how the eye focuses light and helps an eye-care professional determine whether a refractive error is affecting vision.
Refractive errors include short-sightedness (myopia), long-sightedness (hyperopia), astigmatism and, in many adults, presbyopia. These conditions can cause blurred or reduced clarity of vision when the eye does not focus light appropriately on the retina.
What happens during a refraction?
During a refraction, you may be asked to look at letters, symbols or other targets while viewing through different lenses. The eye-care professional changes the lens power and asks which option provides clearer or more comfortable vision.
The assessment may involve an instrument-based measurement followed by a subjective refraction in which you provide responses about the clarity of different lens choices.
The process is non-invasive and usually does not cause pain. Depending on the person's age, symptoms and clinical circumstances, other parts of an eye examination may also be performed.
What can refraction help identify?
Refraction can help identify the type and degree of refractive error affecting vision and can help determine an appropriate optical prescription.
The result can be used to prescribe glasses or contact lenses when these are appropriate. The prescription may differ between the two eyes.
What does a refraction result mean?
A refraction result describes the optical correction that may improve visual clarity. The final prescription also takes into account factors such as the person's visual needs, comfort, age and clinical circumstances.
Clearer vision after refraction does not by itself mean that the eyes are healthy. Refraction is one part of an eye examination, and an eye-care professional may recommend additional assessment when symptoms, examination findings or risk factors indicate that it is appropriate.
Refraction evaluates optical focus and helps determine an appropriate prescription. It does not by itself assess all aspects of eye health or exclude eye disease. Clinical interpretation should be considered alongside the broader eye examination and the person's history and symptoms.
References
- Refractive Errors — National Eye Institute
- Refraction — American Academy of Ophthalmology EyeWiki
- Long-sightedness (hypermetropia) — NHS