Overview
EN ISO 18369-4:2017 (ISO 18369-4:2017, corrected version 2017-10-01) is a CEN-adopted international standard for testing the physicochemical properties of contact lens materials. It defines validated test methods, measurement units and reporting requirements for key material characteristics used in both hydrogel and non‑hydrogel contact lenses. The standard is intended for laboratories, suppliers and users who need consistent, traceable test results for quality control, product development and regulatory compliance.
Key Topics and Technical Requirements
The standard covers methods for measuring the following properties and includes associated precision targets:
- Extractables: Procedures for extraction testing to identify mass % of leachable substances (see clause 4.2).
- Rigid lens flexure and breakage: Tests for flexural deformation and rupture of rigid lenses to assess mechanical durability (clause 4.3).
- Oxygen permeability (Dk): Polarographic method as the primary technique, normalization using reference lenses, and expression of oxygen permeability in Dk units (barrer). Repeatability guidance: ~10% for Dk (clause 4.4). Annex A describes the coulometric alternative method.
- Refractive index: Measurement recommendations (Abbe refractometer), test sample preparation and result expression; repeatability guidance 0.01 (clause 4.5). Annex D covers prism‑coupling measurement.
- Water content: Gravimetric loss‑on‑drying procedure for determining water content/absorption; repeatability guidance 2% absolute (clause 4.6). Annex B provides an alternative refractive‑index based determination; Annex C offers calculation guidance for hydrogel Dk based on water content.
- Reporting and repeatability: Standardized test report content and guidance on establishing measurement repeatability in individual laboratories.
Applications and Who Uses It
EN ISO 18369-4:2017 is used by:
- Contact lens manufacturers for material specification, product development and batch release testing.
- Independent testing laboratories for quality control, contract testing and accreditation.
- Regulatory bodies and notified bodies assessing safety and conformity of contact lens materials.
- R&D teams and material scientists evaluating oxygen transmissibility, mechanical durability and hydration characteristics.
- Suppliers of lens materials and components for technical data sheets and declarations.
Practical benefits include harmonized test data for material selection, clearer regulatory submissions, and comparable performance metrics across suppliers and laboratories.
Related Standards
- ISO 18369-1:2017 - Vocabulary, classification and labelling recommendations
- ISO 18369-3:2017 - Measurement methods (related test infrastructure)
- ISO 3696:1987 - Laboratory water quality (referenced for reagents and procedures)
- Other parts of the ISO 18369 series for comprehensive contact lens standards and regulatory alignment.
Keywords: EN ISO 18369-4:2017, contact lens materials, physicochemical properties, oxygen permeability, refractive index, water content, extractables, rigid lens flexure, ophthalmic optics, testing methods.
