Correcting Defects of Vision

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Astigmatism Prescriptions

A prescription for astigmatism contains three terms: S, C and A.

Illustrative background for SIllustrative background for S ?? "content


  • The 'spherical' part of the prescription in dioptres, ie the short or long sightedness correction.
Illustrative background for CIllustrative background for C ?? "content


  • The degree of astigmatism, also measured in dioptres.
Illustrative background for AIllustrative background for A ?? "content


  • The orientation of astigmatism from 0 to 180 degrees.
Illustrative background for Example prescriptionsIllustrative background for Example prescriptions ?? "content

Example prescriptions

  • E.g. -2.00 +1.50 × 180
  • E.g. +3.50 +3.00 × 45

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1Measurements & Errors

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4Mechanics & Materials


6Further Mechanics & Thermal Physics (A2 only)

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8Nuclear Physics (A2 only)

9Option: Astrophysics (A2 only)

10Option: Medical Physics (A2 only)

11Option: Engineering Physics (A2 only)

12Option: Turning Points in Physics (A2 only)

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