Description
Same-curvature refracting-surface power under explicitly supplied indices, without selecting a lens base curve.
Optical calculations distinguish lens power in diopters, prism notation, angular axes, geometric distances, and visual-acuity reporting scales. Sign conventions and length units are especially important when a formula combines power with decentration or vertex distance. A supplied model term is separate from a validated visual test or prescription.
Same-curvature refracting-surface power under explicitly supplied indices, without selecting a lens base curve.
When to use this tool
Use Lens Base Curve Supplied Index Crosswalk when you need this explicit optical, chart, frame, axis, or reference conversion with compatible supplied units.
How to use the tool and how it works
- Enter referenceSurfacePower, referenceIndex, targetIndex. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read targetSurfacePower, curvaturePerMeter. Use the output convention below.
Require positive referenceIndex and targetIndex with referenceIndex!=1. Return curvaturePerMeter=referenceSurfacePower/(referenceIndex-1) and targetSurfacePower=curvaturePerMeter*(targetIndex-1).1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| referenceSurfacePower | Reference Surface Power | Required. Finite number. |
| referenceIndex | Reference Index | Required. Finite number; strictly above 0. |
| targetIndex | Target Index | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| targetSurfacePower | Target Surface Power | Required. Finite number. |
| curvaturePerMeter | Signed inverse radius inferred from supplied reference surface power and index. | Required. Finite number. |
{
"input": {
"referenceSurfacePower": 5,
"referenceIndex": 1.5,
"targetIndex": 1.6
},
"output": {
"targetSurfacePower": 6.000000000000001,
"curvaturePerMeter": 10
}
}Limitations and assumptions
- Surface power is inverse meters under the supplied index-relative-to-air model. Indices below one and signed powers are permitted; the tool does not validate a lens material, combine both surfaces, or establish a usable clinical lens.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the appropriate complete optical or measurement model when a scalar term is insufficient. Verify power, axis, length, notation, and reference conventions before applying the result within a broader assessment.
References
Similar or alternative tools
- Corneal Curvature Radius Diopter Reference
Conventional index-minus-one over radius power using a caller-supplied keratometric index, not true two-surface corneal power.
- Optometric Trial Frame Vertex Reference
Paraxial thin-lens vergence transfer F/(1-dF) through signed distance d, without a patient vertex-distance prescription.