Overview
EN ISO 8624:2020 - Ophthalmic optics: Spectacle frames - Measuring system and vocabulary specifies a standardized measuring system and related terminology for spectacle frames whose fronts are intended to be symmetrical. Published as ISO 8624:2020 and adopted by CEN as EN ISO 8624:2020, this fourth edition updates and clarifies the boxed-lens measurement approach used across the ophthalmic optics supply chain.
Key topics and technical scope
- Boxed lens system - The core measurement method uses rectangular boxes that circumscribe each lens shape; the common upper tangent of the boxes is regarded as horizontal. Measurements can be taken in the plane of the lens shape for frames with a significant face form angle.
- Principal dimensions defined and labelled (examples from the standard):
- Horizontal boxed lens size (a) - distance between vertical sides of the box.
- Vertical boxed lens size (b) - distance between horizontal sides of the box.
- Boxed centre distance (c) - horizontal distance between boxed centres.
- Distance between lenses (d) - horizontal distance between nasal vertical box sides.
- Overall length of side (l) - length of the temple (side) measured from joint axis or lug to end, with guidance for sides with or without a joint.
- Complementary vocabulary - horizontal and vertical centrelines, boxed centre, vertical axis of symmetry, bridge width line (positioned 5 mm below the horizontal centreline), bridge width, bridge height and related definitions.
- 3‑dimensional frames - Annex A (informative) discusses measurement considerations for 3D-shaped spectacle fronts and face form angles.
- Traceability and compatibility - The standard clarifies how measurements relate to groove apex, rimless/semi-rimless constructions, and notes that tolerances for key dimensions are specified elsewhere (e.g., ISO 12870).
Practical applications
- Ensures consistent frame sizing and specification across manufacturers, suppliers and retailers.
- Provides a common vocabulary for technical drawings, quality control, production tolerances and labelling.
- Used in product development, verification, conformity assessment and cross-border trade to reduce ambiguity in frame dimensions.
- Facilitates accurate fitting, lens cutting and mounting by optical labs using standardized boxed-lens dimensions.
Who should use this standard
- Spectacle frame manufacturers and designers
- Optical laboratories and lens mounters
- Quality and compliance teams in ophthalmic product supply chains
- Retailers, optometrists and dispensing practitioners involved in frame specification
- Standards bodies and test laboratories
Related standards
- ISO 12870 (tolerances for frame dimensions) - referenced for dimension tolerances
- ISO 13666 (as-worn pantoscopic angle) - referenced for face form considerations
EN ISO 8624:2020 is essential for anyone needing consistent, standardized measurements and vocabulary for spectacle frames, improving interoperability across design, manufacturing and clinical processes.