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

  • James Thorington
Date:
1899
Catalogue details

Licence: Public Domain Mark

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

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    4. By placing a concave cylinder in front of the double cylinder at an oblique axis, thus getting a picture of compound irregular astigmatism. 5. By placing a concave cylinder in front of the convex sphere and developing astigmatism with the conic cornea, which is the usual condition ; or a con- vex cylinder might be used in place of the concave cylinder if a higher error is desired. 6. It is obvious, also, that the scissor movement can be produced by a prism which is made to cover one-half of the pupillary area, but the resulting picture is not so satisfactory for demonstration as that given by the combination lens referred to in figure 41.
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