Astigmatic lens transpose calculator

Transpose rules

Example prescription: Sph +2.00 D Cyl +1.00 D Ax 90°.

1. New sphere = old sphere + old cylinder.
2. New cylinder = same cylinder value with the opposite sign.
3. New axis = current axis ±90° within the 0–180° range.

Example result: Sph +3.00 D Cyl -1.00 D Ax 180°.

Tip: if axis is 90° or less, add 90°. If axis is above 90°, subtract 90°.

Examples:
-2.00/+1.00 ax 90° ⇄ -1.00/-1.00 ax 180°
+6.00/-0.25 ax 5° ⇄ +5.75/+0.25 ax 95°
+3.50/+3.50 ax 100° ⇄ +7.00/-3.50 ax 10°