Prism Calculator

Patients with diplopia sometimes require simultaneous prism correction of both a horizontal and a vertical deviation. To keep the total prism power as low as possible, it is advantageous to prescribe oblique prisms.

This calculator determines the power and base of the resulting oblique prism and lets you distribute the total power freely between the two eyes. It can also resolve an oblique prism into its horizontal and vertical components, and convert prism diopters (cm/m) into degrees of deviation and vice versa.

The calculator can be installed as an app and then also works offline. Click the install icon in the address bar of Chrome or Edge (or choose “Install app” from the browser menu). On iPhone and iPad, open this page in Safari, tap “Share” and then “Add to Home Screen”.