Prentice position

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The Prentice Position is a term, from Optics and Ophthalmology. A ray of light incides on a prism at an angle of 90° to the first interface, so that the beam does not deviate at that face. All the deviation caused by the prism takes place at the exit interface.

Plastic prisms and prism bars are made so they are held at the Prentice position. However, this is only true if the person examined has ortho alignment.

Classically, the Prentice position is used only for glass prisms. [1] This is where the prism is perpendicular to the line of sight. With plastic prisms, the prism is held in the frontal position.

[edit] References

  1. Clinical Optics Third Edition by A.R. Elkington, H.J. Frank and M. J. Greaney ISBN 0-632-04989-8
  1. ^ [1] Ophthalmic prisms. Measurement errors and how to minimize them. by Thompson JT, Guyton DL in Ophthalmology: 1983 Mar;90(3):204-10.