Historical
DIN EN ISO 21987:2010
Ophthalmic optics - Mounted spectacle lenses (ISO 21987:2009); German version EN ISO 21987:2009
This International standard establishes requirements for finished, mounted prescription eyewear for refractive power, prismatic power, prism imbalance and prism reference point placement and mechanical tolerances of segment/fitting cross placement.
Deutsches Institut für Normung [din]