Overview
ISO 8624:2020 - Ophthalmic optics - Spectacle frames: Measuring system and vocabulary defines a standardized measuring system and terminology for spectacle frames. The standard applies to frames whose fronts are intended to be symmetrical and provides consistent definitions for the dimensions and reference planes used when measuring frame and lens apertures. An informative annex (Annex A) addresses measurement of three‑dimensionally shaped frames (face form/wrap).
Key topics and requirements
The document establishes the boxed lens system as the basis for measurements and introduces clear terms and symbols used throughout the optical and eyewear supply chain. Major technical topics include:
- Boxed lens system - rectangular boxes that circumscribe lens shapes; the upper tangent is common to both lenses and regarded as horizontal.
- Primary dimensions:
- Horizontal boxed lens size (a) and vertical boxed lens size (b) - lens aperture sizes measured in the plane of the lens shape.
- Boxed centre distance (c) and Distance between lenses (d) - horizontal relationships between the two lens boxes.
- Overall length of side (l) - temple (side) length measurement method, with instructions for sides with and without joints.
- Bridge measurements:
- Bridge width line (5 mm below horizontal centreline), bridge width, and bridge height - definitions and measurement references for pad and rim configurations.
- Additional concepts:
- Frame effective diameter - minimum circular uncut lens size that can be edged to the lens shape.
- Lens shape - definition of the outermost lens edge to be used for measurements.
- Plane definitions and face form angle - plane of spectacle front, plane of lens shape, and wrap (face form) angle measurement.
- Clarifications for rimless/semi‑rimless frames and how groove apex or mounted afocal lens edges serve as measurement references.
- Inclusion of minor nasal asymmetry handling (bridge height) and an informative annex for 3D frame measurement.
Applications and users
ISO 8624:2020 is used to ensure consistent, repeatable measurements and vocabulary across the ophthalmic industry. Typical users include:
- Eyewear manufacturers and designers - for frame specification and design documentation.
- Lens laboratories and edging centres - to determine effective diameter and lens blank requirements.
- Optical retailers, opticians and fitters - to communicate frame sizes and bridge/temple dimensions to customers.
- Quality control and testing laboratories - for inspection, conformity and interchangeability checks.
- Product data teams and e‑commerce platforms - for accurate size metadata and filter attributes.
Related standards
- ISO 12870 (tolerances on spectacle frame dimensions) is referenced in relation to tolerances for key dimensions.
- ISO 13666 (as‑worn pantoscopic angle) is relevant for geometric orientation when frames are worn.
Keywords: ISO 8624:2020, ophthalmic optics, spectacle frames, measuring system, boxed lens system, frame dimensions, face form angle, bridge width, effective diameter, lens shape.