Refraction refers to the bending of light as it passes through one medium to another with a different density, such as passing from air to the cornea of the eye. In the context of an eye exam, refraction refers to the measurement of a person’s refractive error, which is the degree to which their eye has difficulty focusing light on the retina.
During a refraction test, the eye doctor will use a device called a phoropter, which contains a series of lenses of varying strengths. The person undergoing the exam looks through the phoropter while the doctor switches between different lenses, asking the person which lenses provide the clearest vision.
Based on the person’s responses, the doctor can determine the prescription needed for corrective lenses such as eyeglasses or contact lenses to help them see more clearly. The prescription is typically expressed in diopters, which represents the degree of refraction needed to correct the person’s vision.
Common refractive errors include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism, all of which can be corrected with prescription eyewear or other vision correction treatments. Refraction is an important part of a comprehensive eye exam and can help identify and correct vision problems to improve a person’s quality of life.