Vertex Distance Power Conversion
Vertex-corrected power = Fs / (1 - d·Fs), converting spectacle-plane power to the corneal plane; clinically significant beyond about +/- 4 D.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Spectacle-plane power
- 5 D
- Vertex distance
- 12 mm
Result: Vertex-corrected power 5.32 D.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- any power
- Corrects spectacle-plane power to the corneal plane; clinically significant beyond about +/- 4 D. Round to 0.25 D. An optical value, not a diagnosis.
What you enter
- Spectacle-plane power
- Vertex distance
How this is calculated
Vertex distance power conversion, Fc = Fs / (1 - d·Fs) (geometric optics; see Wikipedia "Vertex distance" and standard refraction texts). Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.