Overview
EN ISO 21987:2017 - Ophthalmic optics: Mounted spectacle lenses specifies requirements and test methods for mounted spectacle lenses in relation to the prescription order. Published by CEN and identical to ISO 21987:2017, this standard defines how finished (mounted) corrective lenses should meet optical, mechanical and marking requirements and how conformity is verified. It also aligns with EU medical-device essential requirements (Annex ZA / Directive 93/42/EEC).
Key topics and technical requirements
The standard addresses the full production-to-delivery lifecycle for mounted spectacle lenses with emphasis on verification against the prescription:
- Scope & classification: Definitions and classes of mounted spectacle lenses covered by the standard.
- Optical requirements: Verification of back vertex power, cylinder axis direction, addition/variation power (multifocal and power-variation lenses), and prism imbalance (relative prism error).
- Positioning & thickness: Requirements for correct placement of multifocal segments, position-specific single-vision lenses and limits related to lens thickness.
- Polarizing lenses: Orientation requirements and methods to verify planes of transmission.
- Verification methods: Clause-based test procedures for power, axis, addition/variation, prism imbalance, position and tilt, and material/surface inspection.
- Marking & identification: Mandatory permanent marking for position-specific and power-variation lenses plus optional non-permanent marking.
- Recommendations: Best-practice guidance on mounting and inspection (informative annexes on material/surface quality and mounting).
- Conformance to EU rules: Informative Annex ZA maps standard clauses to the essential requirements of Directive 93/42/EEC (medical devices).
Practical applications
EN ISO 21987:2017 is used to ensure that finished spectacles match the eye-care professional’s prescription and meet safety, optical performance and regulatory expectations. Typical applications include:
- Quality control and final inspection in lens fabrication and eyewear assembly
- Test methods for laboratories verifying mounted lens parameters
- Compliance documentation for manufacturers seeking conformity with EU medical-device requirements for corrective lenses
Who should use this standard
- Spectacle lens manufacturers and laboratories
- Optical laboratories and dispensers fitting and finalizing spectacles
- Quality managers and compliance officers in ophthalmic optics
- Regulatory bodies and conformity assessment organizations
Related standards
Normative and related references cited include ISO/EN standards commonly used together with EN ISO 21987, for example: ISO 7944, ISO 8429, ISO 8598-1, ISO 8624, ISO 8980-1, ISO 8980-2, ISO 13666, ISO 14889. These address test methods, lens properties and additional ophthalmic optics requirements.
Keywords: EN ISO 21987:2017, mounted spectacle lenses, ophthalmic optics, verification methods, prism imbalance, multifocal lenses, position-specific lenses, optical requirements.
