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Vertex Distance Calculator
Compensate lens power for vertex distance changes
When to use this calculator:
- Converting spectacle Rx to contact lens Rx (use 0mm for new vertex)
- Frame changes with different vertex distances
- High prescriptions (4.00D or greater)
Enter Prescription
Use negative for minus powers, positive for plus
mm
mm
Common Conversions:
Result
Enter a lens power and calculate to see the compensated result
Quick Reference Table
| Spectacle Rx (12mm) | Contact Lens Rx (0mm) | Difference |
|---|---|---|
| -4.00 D | -3.75 D | +0.25 D (less minus) |
| -6.00 D | -5.50 D | +0.50 D (less minus) |
| -8.00 D | -7.25 D | +0.75 D (less minus) |
| -10.00 D | -8.75 D | +1.25 D (less minus) |
| +4.00 D | +4.25 D | +0.25 D (more plus) |
| +6.00 D | +6.50 D | +0.50 D (more plus) |
Note: Values are approximate. Always verify with exact calculations for patient prescriptions.