Overview
EN ISO 18369-2:2017 (Ophthalmic optics - Contact lenses - Part 2: Tolerances) is a CEN-adopted ISO standard that defines the manufacturing tolerance limits for the principal optical and physical parameters of rigid corneal, rigid scleral and soft contact lenses. The standard specifies how dimensional, optical and some material property tolerances are to be interpreted and tested at the time of manufacture. It also clarifies that these tolerance limits might not apply for other purposes (for example, shelf‑life studies).
Key topics and requirements
- Scope of tolerances: Dimensional and optical tolerances for rigid and soft lenses (e.g., back optic zone radius/base curve, sagittal depth, total diameter, centre thickness, back vertex power, cylinder power and axis).
- Testing and conditioning: Lenses shall be equilibrated in standard saline or packaging solution prior to measurement as described in the referenced test methods.
- Conformance criteria: The standard describes three approaches to demonstrate conformance - 100% inspection, acceptance sampling, and statistical estimation of performance (process assessment).
- Finish and cosmetic quality: Requirements for inclusions, surface imperfections, fenestrations and edge contour when examined under magnification (minimum 7×).
- UV transmittance: Rules for classifying and measuring lenses that claim ultraviolet attenuation (Class 1 or Class 2 absorbers).
- Deviations and risk justification: For stock soft lenses, manufacturers can deviate from the listed tolerances only when supported by clinical data (ISO 11980) and a risk assessment (ISO 14971). Custom lenses are treated separately.
- Reference test methods: Measurement methods are specified in related documents (notably ISO 18369-3 and ISO 18369-4).
Applications and who uses this standard
EN ISO 18369-2:2017 is practical for:
- Contact lens manufacturers - to define production tolerances, quality specifications and design files.
- Quality assurance and production engineers - for setting inspection plans (100% inspection or sampling) and acceptance criteria.
- Independent testing laboratories - for verifying dimensional and optical compliance using ISO test methods.
- Regulatory and conformity assessment bodies - to evaluate product claims and evidence of conformance.
- Clinicians and procurement specialists - to understand expected manufacturing variability when selecting stock or custom lenses.
Related standards
- ISO 18369-1 - Vocabulary, classification and labelling recommendations
- ISO 18369-3 - Measurement methods (referenced for all tests)
- ISO 18369-4 - Physicochemical properties of contact lens materials
- ISO 11980 - Clinical data guidance (when justifying deviations)
- ISO 14971 - Risk management for medical devices
Keywords: EN ISO 18369-2:2017, contact lens tolerances, ophthalmic optics, manufacturing tolerances, rigid contact lenses, soft contact lenses, ISO 18369 series, contact lens testing.
