Optical Calculators
Spectacle Magnification/Aniseikonia Calculator
See how much a lens magnifies or minifies, so you can identify and correct aniseikonia when a patient's two prescriptions are very different. Enter the Rx, vertex distance, base curve, center thickness and material.
Every lens changes image size. Spectacle magnification has two parts: the power factor, which comes from the Rx and vertex distance, and the shape factor, which comes from the base curve, center thickness and material.
Inputs:
- Rx (sphere, cylinder, axis): plus lenses enlarge, minus lenses shrink.
- Fitted vertex distance
- Base curve and center thickness: these change image size without changing the Rx.
- Lens material
Results show magnification as a percentage, broken into spherical, cylindrical, horizontal and vertical parts. Cylinder magnifies more in one direction than the other, which is why the breakdown matters.
To balance image size between the eyes, adjust the base curve, thickness or vertex distance of one lens until the two match. That can ease double vision, distortion and eye strain.
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