BS 2738-1:1998

Committees responsible
Foreword
1 Scope
2 Normative references
3 Definitions
4 Classification
5 Requirements
6 Permanent marking of progressive power lenses
7 Test methods
Annex A (informative) Recommendations regarding subjective
characteristics of spectacle lenses
Annex B (informative) Method for evaluating progressive power
lens characteristics
Bibliography
Figure 1 Use of a focimeter to measure the addition power
of a front surface multifocal or progressive power lens
Figure 2 Measurement of the addition power
Figure A.1 Recommended system for visually inspecting a lens
for defects
Figure A.2 Front view of round lenses illustrating marks
(exaggerated) on back surfaces denoting right and left
Figure B.1 Measurement of the optical characteristics in the
as-worn position
Tables
1 Tolerances on the back vertex power of single-vision and
    multifocal lenses
2 Tolerances on the back vertex power of progressive power
    lenses
3 Tolerances on the direction of the cylinder axis
4 Tolerances on the addition power for multifocal and
    progressive power lenses
5 Centration tolerances
6 Prism tolerances

Defines, with reference to the prescription order, tolerances for properties of mounted spectacle lenses. Does not apply to the transmission properties of tinted, coated or otherwise treated lenses, nor to material from which the lens is made.