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Prentice's Rule calculator

Induced prism (Δ) = decentration (cm) × lens power (D). Enter the values for one lens.

Use the lens power in the meridian of decentration. For a sphere lens, that's simply the sphere power.

Use a minus sign for minus lenses, e.g. −3.00
Horizontal decentration
Vertical decentration
Reading through the lower part of the lens means the OC is above the pupil.
Independent study resource

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