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Vertex-distance optical conversion — not a prescription

Paraxial optics in air, transferring both principal meridians separately to the corneal plane; axis is unchanged. Excludes tear-lens effects, materials, fitting and available-power rounding. Not a contact-lens prescription or ordering recommendation. Input bounds are computational limits.

Paraxial optics in air, transferring both principal meridians separately to the corneal plane; axis is unchanged. Excludes tear-lens effects, materials, fitting and available-power rounding. Not a contact-lens prescription or ordering recommendation. Input bounds are computational limits.

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Result

Enter your values and run the tool to see your result.

How to use this tool

Check the units, enter your values, and run the tool. Results follow the assumptions and method below.

Calculation method

First principal meridian at corneal planesphere/(1-vertex/1000*sphere)
Second principal meridian at corneal plane(sphere+cylinder)/(1-vertex/1000*(sphere+cylinder))
Equivalent principal-meridian power difference(sphere+cylinder)/(1-vertex/1000*(sphere+cylinder))-sphere/(1-vertex/1000*sphere)

References