According to Prentice's rule, the amount of induced prism is equal to which of the following?

• A. Lens power times the thickness
• B. Lens power times the decentration in millimeters divided by 10
• C. Decentration times thickness
• D. Lens power divided by the decentration

Answer: (B)

Prentice's rule focuses on calculating the amount of induced prism when a lens is decentered. According to this rule, the amount of induced prism (measured in prism diopters) is indeed determined by multiplying the lens power (in diopters) by the degree of decentration (in millimeters) and then dividing by 10. This is because 1 diopter of power induces 1 prism diopter of deviation when shifted 10 millimeters from the optical center.

This relationship highlights how the physical properties of the lens and its placement in front of the eye create a specific visual effect in terms of prism. It’s essential for practitioners to understand this calculation because proper alignment of lenses is critical in optical prescriptions and their effectiveness in correcting vision.

The other options present incorrect or incomplete interpretations of how induced prism is calculated based on Prentice's rule. Understanding the correct formula allows for accurate applications in various practical settings, such as in fitting glasses or when evaluating the effects of lens positioning.