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Eyeglass prescription transposition explorer

Convert a spectacle prescription between plus-cylinder and minus-cylinder notation, then check the optical cross, principal meridian powers, and spherical equivalent without reaching for a paper worksheet.

Target search intent: prescription transposition calculator, plus cylinder to minus cylinder, minus cylinder to plus cylinder, spherical equivalent calculator.

Educational use for interpreting an existing spectacle prescription. It does not create or recommend a new prescription.

Prescription summary

Results update instantly as you type, and the optical-cross view proves the meridian powers stay the same after transposition.

Core numbers

The transposed notation changes the written form, not the lens power in each principal meridian.

Optical cross

Axis meridian and power meridian should match in both written forms.

Why this works

  • New sphere = old sphere plus the signed cylinder.
  • New cylinder = same magnitude with the opposite sign.
  • New axis = old axis rotated by 90°, wrapped back into the 1-180 range.
  • Spherical equivalent = sphere plus half the signed cylinder.

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