Overview
EN ISO 18369-3:2017 - "Ophthalmic optics - Contact lenses - Part 3: Measurement methods" (ISO 18369-3:2017) defines standardized laboratory and inspection methods for measuring the physical and optical properties of finished contact lenses. Adopted by CEN, this second edition (2017) supersedes the 2006 version and is intended for testing laboratories, manufacturers, suppliers and regulators involved in contact lens quality control and compliance.
Key topics and requirements
- Scope of measurement: Methods for determining key contact lens parameters specified in ISO 18369‑2, including
- Radius of curvature (optical spherometry, ophthalmometer; sagittal depth methods for hydrogels)
- Label back vertex power (focimeter specifications, calibration, measurements for rigid and hydrogel lenses)
- Diameter and zone widths
- Thickness (dial gauge and low‑force mechanical gauge methods)
- Edge inspection, inclusions and surface imperfections
- Spectral transmittance (instrument and test conditions)
- Equilibration and test solution: Specifies the equilibrating solution and a standard saline solution formulation and preparation for conditioning lenses prior to testing.
- Measurement performance: Methods should achieve repeatability and reproducibility (R&R) such that R&R ≤ 30% of the allowed tolerance range. Lenses must be equilibrated until measured parameters are stable within the method’s capability.
- Ancillary requirements: Focimeter calibration, specific temperature considerations during equilibration and measurement, and documentation of the equilibration procedure in test reports.
- Informative annexes: Additional measurement techniques and guidance are provided (e.g., interferometry for rigid lens curvature, Moiré/Hartmann methods for soft lenses, ophthalmometer use, and focimeter paddles).
Applications and users
- Contact lens manufacturers: Routine production quality control, specification verification and incoming inspection.
- Testing and calibration laboratories: Accredited testing against standardized methods for compliance and certification.
- Suppliers and distributors: Verification of labelling claims (back vertex power, diameter, etc.) and product acceptance testing.
- Regulatory bodies and conformity assessors: Objective, repeatable methods to demonstrate compliance with product standards and safety requirements.
- Research and development: Comparing materials and designs using standardized measurement protocols (radius, thickness, transmittance).
Related standards
- ISO 18369-1:2017 - Vocabulary and labelling (referenced for terms)
- ISO 18369-2 - Contact lens specifications (parameters measured by Part 3)
- ISO 9342-1 and ISO 3696 - Normative references for focimeter test lenses and water quality for test solutions
EN ISO 18369-3:2017 is essential for anyone involved in the measurement, quality assurance and regulatory compliance of contact lenses, ensuring consistent, traceable and internationally harmonized test methods.
