n. an instrument used to determine the power of spectacle lens required to correct *refractive errors of the eye. It is held in the hand and casts a beam of light into the subject’s eye. The examiner looks along the beam and sees the reflection in the subject’s pupil. By interpreting the way the reflection moves as the instrument is moved, and by altering this by lenses held in the other hand near the subject’s eye, the examiner is able to determine the degree of refractive error. —retinoscopy n.
A type of vision test in which a beam of light is shone from an instrument called a retinoscope into each eye in turn. The effect of different lenses on the beam of light determines whether glasses are needed for various refractive errors, such as hypermetropia, myopia, or astigmatism. Retinoscopy is particularly useful for assessing babies or young children.... retinoscopy
(refractometer) n. an instrument for measuring the *refraction of the eye. An autorefractor calculates the required spectacle lens correction automatically. Because the design and use of optometers is very complex, errors of refraction are usually determined using a *retinoscope.... optometer
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