Before revision: Prentice's rule Prentice's rule, named so after the optician Charles F. Prentice, is a formula used to determine the amount of induced prism in a lens: where: P is the amount of prism correction (in prism dioptres) c is decentration (the distance between the pupil centre and the lens's optical centre, in millimetres) f is lens power (in dioptres) The primary use of Prentice's rule is that under certain circumstances, the prescribed prism can be obtained without grinding the prism into the lenses, by decentering the lenses as worn by the patient.
After revision: Prentice's rule Prentice's rule, named so after optician Charles F. Prentice, is a formula used to determine the amount of induced prism in a lens: where: P is the amount of prism correction (in prism dioptres) c is decentration (the distance between the pupil centre and the lens's optical centre, in millimetres) f is lens power (in dioptres) The primary use of Prentice's rule is that under certain circumstances, the prescribed prism can be obtained without grinding the prism into the lenses, by decentering the lenses as worn by the patient.