The refractive power of spectacle lenses is one of the parameters to be considered when designing and fitting spectacles to correct refractive errors. The optical power of an eyeglass lens is the reciprocal of the focal length of the lens and is measured in diopters in SI units, equivalent to m -1.
To measure optical power, a commonly used instrument is a lens meter. This device is designed for measuring the front and rear diopters of ophthalmic lenses.
The accuracy and quality of the measurements taken with this device cannot be overemphasized because of the need to ensure that the lens has the desired optical power. Like any measuring device, lens gauges have associated measurement uncertainties, which can be learned through calibration.
Calibration of this device allows us to ensure that the measurements related to the optical power provided by the lens meter are correct. Regular calibration also allows timely detection of errors or drifts in the equipment related to use, component aging, etc.
The UNE-EN ISO 9642-1 standard specifies recommendations to be considered when calibrating shot timings to ensure traceability of measurements. To calibrate this device, it is necessary to have recognized standards traceable to international measurement systems. As such, standard lens assemblies or sets that can be used to calibrate lensmeters also need to be calibrated by an accredited laboratory.
