Overview
ISO 21987:2017 - Ophthalmic optics - Mounted spectacle lenses specifies the requirements and test methods for spectacle lenses after they have been mounted in frames, relative to the prescription order. This second edition (2017) replaces the 2009 edition and defines how mounted single‑vision, multifocal and power‑variation lenses are verified and classified for optical performance and positioning.
Key topics and technical requirements
- Scope and classification
- Covers finished, mounted lenses classified as single‑vision, multifocal, and power‑variation (e.g., progressive and degressive lenses).
- Optical verification
- Measurement using a focimeter conforming to ISO 8598‑1.
- Verification at the reference point(s) and at reference wavelengths defined in ISO 7944.
- Use of a manufacturer‑provided verification power where applicable; tolerances and ranges are applied to that verification power.
- Principal parameters
- Back vertex power tolerances at reference points (single‑vision and distance reference of multifocals).
- Cylinder axis direction and cylindrical power verification.
- Addition / variation power checks for multifocal and power‑variation lenses (primary and secondary reference points).
- Prism imbalance (relative prism error) limits for mounted lenses, with alternative measurement methods described.
- Positioning and marking
- Requirements for correct positioning and tilt for multifocals and position‑specific single‑vision lenses.
- Permanent and optional non‑permanent marking rules for lenses that require accurate alignment.
- Other requirements
- Thickness, orientation for polarizing lenses, material and surface quality, and recommended mounting practices.
- Environmental reference
- Tolerances apply at a reference temperature of 23 °C ± 5 °C.
- Verification and test methods
- Detailed methods in Clause 6 (focimeter measurement, prism checks, polarizer plane verification, inspection for surface/material quality).
Applications and who uses it
ISO 21987:2017 is essential for:
- Spectacle lens manufacturers - to define finished mounted lens acceptance criteria.
- Eyewear laboratories and opticians - to verify that mounted spectacles meet the ordered prescription and tolerances.
- Quality managers and compliance teams - to implement consistent test methods and documentation.
- Regulatory bodies and procurement - to reference standard measurement and marking requirements.
Practical uses include final quality checks on assembled spectacles, acceptance testing, dispute resolution on prescription fulfillment, and establishing in‑lab processes for focimeter verification.
Related standards
Keywords: ISO 21987:2017, mounted spectacle lenses, ophthalmic optics, focimeter, back vertex power, prism imbalance, multifocal, progressive‑power lenses, verification power.
