We use these things every day. Rather than hoard them in our own private Excel spreadsheets, we’re sharing them with the world! P.S. The world may not find them very useful. When processing lenses in the US, we make some assumptions about index of refraction that seem crazy to the rest of the world.

Converts Plus to Minus Cylinder Form

Converts diopter measurements to radius of curvature

Find the right base curve/thickness combination

See how change in vertex distance changes the effective power perceived by the patient.

Calculate the Sagitta of an arc