Retinoscopy (or shadow test) in the determination of refraction at one meter distance, with the plane mirror / by James Thorington.

  • Thorington, James, 1858-1944.
Date:
1912
Catalogue details

Licence: In copyright

Credit: Retinoscopy (or shadow test) in the determination of refraction at one meter distance, with the plane mirror / by James Thorington. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    and the observer at one meter distance with his plane mirror, the two light areas characteristic of the scissor movement, with their comparatively straight edges and dark interspace may be seen approaching each other from above and below (and the dark interspace disappear- ing) as the mirror is tilted in the vertical meridian. Figures 57 and 58 represent a section of thin plane glass mounted as in Figure 55 and has cemented at its center a small plano-convex sphere of three diopters, whose base 1 + ao(| ) Fig. 55. Fig. 57. Fig. 59. is about four mm. in diameter. Placing this lens in front of the schematic eye at emmetropia, and reflecting the light from the plane mirror at one meter, there will be seen in the pupillary area a small central illumination, which moves against or opposite to the movement of the mirror, and at the same time there will also be seen a peripheral ring (at the edge of the iris) which moves rapidly with the movement of the mirror; between these light areas is a shaded ring of feeble illumination. This is the retino- scopic picture and movement of the light areas, so indica- tive of conic cornea. It is also an exaggerated picture of negative aberration. Figures 59 and 60 represent a section similar to that shown in Figures 57 and 58, except that at its center is