Reference
Calculators
Check your working. Where the workbook’s exam method and exact optics give different answers, both are shown; exam answers follow the exam method.
Lens power
Transpose, find the spherical equivalent, classify astigmatism and read the power in any meridian on an optical cross.
Open lens power calculatorPrism
Prentice's rule by the exam method beside the exact result, the decentration needed for a prism, and oblique prism.
Open prism calculatorVertex distance
Dioptric change, effective and compensated power for spectacles or contact lenses, exam method beside exact.
Open vertex distance calculatorDispensing
Frame PD, decentration per lens from a binocular or monocular PD, minimum blank size and seg or OC placement.
Open dispensing calculator