{"tema_id":"2038","string":"vertex power           #01130","created":"2022-12-19 09:13:41","code":null,"modified":"2022-12-19 13:55:38","notes":[{"@type":"Scope note","@lang":"en-EN","@value":"(1) The unit for expressing vertex power is the reciprocal metre (m-1). The name for this unit is the \u201cdioptre\u201d, for which the symbol is D.(2) Conventionally the back vertex power, in dioptres, is specified as the \u201cpower\u201d of a spectacle lens, although the front vertex power is required for certain purposes (for example in the measurement of some multifocal lenses). "},{"@type":"Cataloger's note","@lang":"en-EN","@value":"reference: R093:1999 3.7 "},{"@type":"Cataloger's note","@lang":"en-EN","@value":"ID: 01130 "},{"@type":"Definition note","@lang":"en-EN","@value":"there are two vertex powers of a lens, described in 3.7.1 and 3.7.2 "}]}