Overview
EN ISO 11978:2017/A1:2020 - Ophthalmic optics: Contact lenses and contact lens care products - Labelling (Amendment 1) is a CEN-endorsed amendment to ISO 11978:2017. It updates labelling requirements to improve legibility and accessibility of manufacturer information on contact lenses and care-product packaging. The amendment (published October 2020) was adopted as a European Standard (EN ISO 11978:2017/A1:2020).
Key topics and technical requirements
- Minimum character/symbol size: All user-facing written information and symbols must be designed with a minimum height of 0.7 mm.
- Contrast requirements: For colour combinations other than black text on a white background, labels must achieve a contrast ratio of at least 3:1 between text/symbol colour and background.
- Colour space and conversions: Colour contrast calculations are to be performed using RGB / sRGB values. CMYK print values should be converted to RGB using a suitable conversion tool.
- Contrast computation method: Annex A (informative) defines the calculation workflow:
- Normalize 8‑bit RGB values to sRGB, apply nonlinear linearization (threshold ~0.04045 and gamma ≈2.4).
- Compute relative luminance using IEC coefficients (L = 0.2126·R + 0.7152·G + 0.0722·B in linear sRGB).
- Calculate contrast as (L1 + 0.05) / (L2 + 0.05), where L1 is the lighter luminance. Black on white has a maximum contrast of 21:1.
- Guidance and examples: Annex A includes worked examples of acceptable and unacceptable colour combinations and references standards/guidelines such as IEC 61966-2-1 and WCAG 2.1.
Applications and who should use it
- Contact lens and care-product manufacturers - to ensure packaging and instructions meet legibility and accessibility requirements for market access in CEN countries.
- Regulatory and compliance teams - to verify label conformity during product approval and audits.
- Packaging designers and print vendors - to select colour schemes, fonts and print processes that meet the 0.7 mm size and 3:1 contrast constraint after CMYK-to-RGB conversion.
- Quality assurance and testing labs - to perform contrast measurements and provide evidence of compliance.
- Optical retailers and healthcare providers - to understand label standards for patient safety and product information clarity.
Related standards
- IEC 61966-2-1 (sRGB / colour management)
- WCAG 2.1 (Web Content Accessibility Guidelines) - referenced for contrast methodology and accessibility principles
- CIE 1931 (colour spaces / tristimulus values)
Keywords: EN ISO 11978, contact lens labelling, ophthalmic optics standard, label contrast ratio, sRGB contrast calculation, CMYK to RGB conversion, packaging compliance, accessibility.