An instrument with various lenses, used to measure the refraction of the eye.
An instrument used to determine the power of ‘refraction 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 shadows it produces in the subject’s pupil. By interpreting the way the shadows move when he moves the instrument, and by altering them by lenses held in his other hand near the subject’s eye, he is able to detect far- or near-sightedness or astigmatism and to determine its degree.
A device used to assess the refractive status of the eye by directing light onto the retina via a mirror.
A device used to assess the eye’s refractive ability.