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Updated April 09, 2014

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Definition: Refraction is the part of an eye or vision exam in which the eye doctor determines your need for prescription glasses. He or she refracts your vision by using a phoropter, a device that contains hundreds of combinations of lenses, to determine any possible refractive error such as nearsightedness, farsightedness, astigmatism, or presbyopia.

Several methods may be used for refraction, but most people are familiar with the type of refraction in which the doctor asks, "Which lens is clearer or better -- lens one or lens two, or do they appear about the same?"

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