Vertex distance conversion
Converts spectacle power to the effective power at the cornea (contact lens) and back.
Inputs
0 of 2D
mm
When to use
- Fitting contact lenses from a spectacle prescription above about ±4.00 D.
Pearls and pitfalls
- Convert each principal meridian separately for astigmatic prescriptions.
Why use
Both directions with the worked optics.
- where
- F1
- Spectacle power, D
- F2
- Power at the cornea, D
- d
- Vertex distance, m