Adjust glasses prescription for contact lenses based on vertex distance.
Input Parameters
Calculation Results
Enter parameters to calculate
Quick Reference
F꜀Contact Lens Power
FₛSpectacle Lens Power
dVertex Distance (in meters)
DDiopters
Overview
The power of a lens changes as it is moved closer to or further from the eye. Vertex distance is the distance between the back surface of a spectacle lens and the front of the cornea.
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Pro Tips
Vertex distance is typically about 12mm to 14mm for glasses.
Adjustment is usually only necessary for prescriptions stronger than +/- 4.00 diopters.
Negative (myopic) powers become less negative (weaker) when moved closer to the eye.
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Fun Facts
"Contact lenses have a vertex distance of 0mm because they sit directly on the eye."
"Nearsighted people need a weaker prescription in contacts than in glasses."
"Farsighted people need a stronger prescription in contacts than in glasses."
