Legislation: Revised British Standards

Ronald Rabbetts updates us on the latest revision to British Standards relating to spectacle lenses

Three revised British Standards relating to spectacle lenses were published last year. They are:

The three standards were revised by the same project group, with the mounted lens standard being taken as the lead. Significant effort was made to use the same verbal descriptions across all three standards, for example in measurement of the addition. More detailed instructions are included for those readers who may be less familiar with using focimeters, manual or automatic.

The new terms ‘power-variation lens’, ‘primary reference point’ and ‘secondary reference point’ have been introduced to simplify the instructions for power measurement in BS EN ISO 21987 and 8980-2. Instead of saying ‘the tolerances apply to the distance portion of a progressive-power lens and the near portion of a degressive-power lens’, these now say that ‘the back vertex power at the primary reference point of power-variation lenses shall comply with the tolerances in Table 2.’

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