Optical transposition calculator.
Convert a spectacle prescription between plus-cylinder and minus-cylinder form — sphere, cylinder and axis, both eyes. Type the numbers, read the answer. Nothing to sign up for.
Enter a prescription above and the transposed form appears here.
How transposition works
The same lens can be written two ways. Transposing converts between them without changing the lens at all — useful when a prescription arrives in plus-cyl from a clinic and your lab orders in minus-cyl, or the other way round.
- 01Add the cylinder to the sphere. That sum becomes the new sphere.
- 02Flip the sign of the cylinder. The power is the same, written the other way.
- 03Rotate the axis by 90°. Add 90 if the axis is 90 or under, subtract 90 if it is over. Axis runs 1–180, so a result of 0 is written as 180.
Worked example
−2.00 / −0.75 × 180
becomes
−2.75 / +0.75 × 90
Both lines describe an identical lens. Always re-check the axis after transposing — an axis error is the one mistake that reaches the patient as a remake.
Your POS should do this for you.
In Optician Dynamics the prescription transposes itself at the counter, saves to the patient record, and prints on the receipt — with the lab order already routed.
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