Rx Transpose

Convert between minus-cylinder and plus-cylinder notation. Axis normalised to 0–180°.

Prescription

Original

+2.00 −1.00 × 180°

Transposed

+1.00 +1.00 × 90°

Both cylinder forms

Minus cylinder

+2.00 −1.00 × 180°

Plus cylinder

+1.00 +1.00 × 90°

Calculation

  1. 01Input: +2.00 −1.00 × 180°
  2. 02Sphere: +2.00 + (−1.00) = +1.00
  3. 03Cylinder: −(−1.00) = +1.00
  4. 04Axis: 180° ± 90° → 90°
  5. 05Result: +1.00 +1.00 × 90°

Both forms describe the same sphero-cylindrical correction. Confirm the notation expected by the receiving system before ordering.

Formula

  1. 01New Sphere = Sphere + Cylinder
  2. 02New Cylinder = −Cylinder
  3. 03New Axis = Axis ± 90° (normalised to 0–180°)

Clinical application

Transposition changes notation only — the refractive correction is identical. Use it when a lab, autorefractor or manufacturer expects a different cylinder convention.

OptiX Pro provides mathematical calculations, reference information, and fitting assistance. It does not replace professional clinical examination, manufacturer fitting guidelines, or professional judgement. Contact lens selection and prescription must be clinically verified.