Lens Transposition Calculator

A tool for optometry students

+/- Cylinder Input

Note: Refresh browser to reset.

Cross Cylinder Input

Note: Axes must be 90 degrees apart. Axis 2 is optional and will default to 90° from Axis 1.

Optical Cross Input

Note: Meridians must be 90 degrees apart. Meridian 2 is optional and will default to 90° from Meridian 1.

Error of Refraction Guide

Determine the error of refraction by looking at the two principal meridian powers on the Optical Cross:

Optical Cross Signs Error of Refraction Examples
(+) and (+) Compound Hyperopic Astigmatism + 2.00 D
+ 1.00 D
(-) and (-) Compound Myopic Astigmatism - 2.00 D
- 1.50 D
(+) and Plano (0.00) Simple Hyperopic Astigmatism + 2.00 D
Plano
(-) and Plano (0.00) Simple Myopic Astigmatism - 2.00 D
Plano
(+) and (-) Mixed Astigmatism + 2.00 D
- 3.00 D
Equal (+) values Hyperopic + 0.25 D
+ 0.25 D
Equal (-) values Myopic - 0.50 D
- 0.50 D