Description
Explicit planar model decentration and conservative circular-blank budget, without selecting spectacle fitting measurements.
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.
Explicit planar model decentration and conservative circular-blank budget, without selecting spectacle fitting measurements.
When to use this tool
Use Spectacle Asymmetric Frame Decentration Pair 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 frameCenterDistance, rightMonocularDistance, leftMonocularDistance, effectiveDiameter. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read rightDecentration, leftDecentration, nominalBlankDiameter. Use the output convention below.
For nonnegative frameCenterDistance, rightMonocularDistance, leftMonocularDistance, and effectiveDiameter return each decentration=frameCenterDistance/2-monocularDistance and nominalBlankDiameter=effectiveDiameter+2*max(abs(rightDecentration),abs(leftDecentration)).1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| frameCenterDistance | Frame Center Distance | Required. Finite number; minimum 0. |
| rightMonocularDistance | Right Monocular Distance | Required. Finite number; minimum 0. |
| leftMonocularDistance | Left Monocular Distance | Required. Finite number; minimum 0. |
| effectiveDiameter | Effective Diameter | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| rightDecentration | Right Decentration | Required. Finite number. |
| leftDecentration | Left Decentration | Required. Finite number. |
| nominalBlankDiameter | Nominal Blank Diameter | Required. Finite number. |
{
"input": {
"frameCenterDistance": 70,
"rightMonocularDistance": 32,
"leftMonocularDistance": 30,
"effectiveDiameter": 50
},
"output": {
"rightDecentration": 3,
"leftDecentration": 5,
"nominalBlankDiameter": 60
}
}Limitations and assumptions
- Lengths need one unit and share the supplied frame-center convention. The nominal diameter excludes additional edging allowance and does not establish correct pupil placement, actual lens shape, or clinical fit.
- 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
- Spectacle Frame Effective Diameter Clearance
Residual circular blank clearance after supplied frame effective diameter, planar decentration and radial allowance.
- Ophthalmology Interpupillary Half Distance Offset
Compare explicit total and monocular distance records, without selecting a spectacle fit or determining patient measurements.