In prism prescribing, what does the abbreviation 'pd' stand for?

In prism prescribing, what does the abbreviation 'pd' stand for?

• A. Prism Diopters
• B. Prism Degrees
• C. Prism Distance
• D. Prism Density

Answer: (A)

In prism prescribing, the amount of prism is expressed in prism diopters, abbreviated pd. This unit measures how much angular deviation a prism would produce so that a ray is shifted by 1 centimeter at a distance of 1 meter. In practical terms, if you prescribe 2 pd base-in, you’re adding two prism diopters of inward prismatic power. Note that pd is sometimes used for pupillary distance in other contexts, but here it refers to prism diopters—the power of the prism.

In prism prescribing, the amount of prism is expressed in prism diopters, abbreviated pd. This unit measures how much angular deviation a prism would produce so that a ray is shifted by 1 centimeter at a distance of 1 meter. In practical terms, if you prescribe 2 pd base-in, you’re adding two prism diopters of inward prismatic power. Note that pd is sometimes used for pupillary distance in other contexts, but here it refers to prism diopters—the power of the prism.