This part of ISO 9342 specifies requirements for test lenses for the calibration of focimeters that are used for the measurement of spectacle form lenses.
NOTE It is accepted that other test lenses can also be used with powers within the given range, manufactured to the same standard of accuracy and form, but different back vertex powers. However, only lenses with integer nominal powers, as described in Annex A, can be used for the calibration of digitally-rounding focimeters.