National Physical Laboratory

Ophthalmic and Spherical Lenses

An important factor in achieving accurate production of spectacle lenses is the maintenance of consistent standards of lens power in the ophthalmic examination, lens manufacture and subsequent spectacle fitting. Consistent measurements of power may be assessed in all these stages by using focimeters and spherometers which have been calibrated with suitable reference lenses.

NPL offers a wide range of services in support of accurate ophthalmic measurements including the calibration of customer supplied reference lenses and the calibration of focimeters.

Calibration services

  • Calibration of the power of reference lenses in the range ± 1 dioptre to ± 25 dioptres, measurement uncertainty ± 0.005 dioptres to ± 0.02 dioptres
  • Calibration of the power of weak lenses in the range ± 0.05 dioptres to ± 1 dioptre, measurement uncertainty ± 0.002 dioptres
  • Power measurements of spherical, cylindrical and prismatic lenses

Key features

  • Fast and reliable service
  • Calibration traceable to national standards
  • NPL certificate of calibration issued

Associated services

  • Calibration of focimeters on and off site
  • Calibration of the optical properties of a gaugemaster
  • Power measurement of contact lenses
  • Assessment of ophthalmic equipment and measuring processes

For further information or to discuss your particular calibration requirements
Contact: Length Services
Direct Line: +44 208 943 6245
Fax: +44 208 943 6184

Last Updated: 25 Mar 2010
Created: 5 Sep 2007


Please note that the information will not be divulged to third parties, or used without your permission