Overview
ISO/TR 21958:2019 is a technical report from ISO/TC 172/SC 7 that reviews the most commonly used test methods for assessing scratch resistance and abrasion resistance of plastic spectacle lenses. Rather than setting new pass/fail criteria, the document describes test principles, procedures, technical capacities and limitations, and includes discussion of the ISO test method used to assess basic abrasion-resistance claims in ISO 8980-5. The report is intended to support future ISO standardization and to inform manufacturers, test laboratories and other stakeholders about the meaning and applicability of different lens durability tests.
Key topics and technical content
- Background and rationale - why plastic lens coatings required new test approaches as markets shifted from glass to plastic.
- Mechanisms of damage - clear discussion of friction-related (scratching) vs impact-related (abrasion) mechanisms and how force, contact area, hardness, friction and surface roughness interact.
- Damage classification - common damage types (tearing, cutting, scuffing, pitting, chipping) and how results differ by mechanism.
- Detailed test-method reviews - descriptions, principles, and pros/cons for the main abrasion/scratch tests considered in standardization:
- Steel wool test
- Tumble test
- Eraser test
- Bayer (oscillating abrasive grain) test
- Nano-scratch (diamond point loading)
- Taber abrasion wheel test
- ISO 8980-5 method for basic abrasion-resistance claims
- Assessment and limitations - evaluation approaches for surface damage, reasons why no single test reliably predicts real-world wearer experience, and the role of ISO 8980-5 in establishing a minimum performance methodology.
- Conclusions and bibliography - summary of findings to guide future work.
Practical applications - who uses this standard
- Spectacle lens and optical-coating manufacturers - to choose appropriate lab tests for R&D and quality control.
- Independent test laboratories and certification bodies - to interpret test results and select suitable methods for different claims.
- Standards developers and regulators - to inform harmonized test protocols and policy on product claims.
- Procurement/specifiers and quality managers - to understand the limitations of marketed “scratch-resistant” claims and to set realistic acceptance criteria.
Related standards
- ISO 8980-5 - Minimum requirements for spectacle lens surfaces claimed to be abrasion-resistant (included and discussed in ISO/TR 21958:2019).
Keywords: scratch resistance, abrasion resistance, spectacle lenses, optical coatings, abrasion testing methods, ISO 8980-5, lens durability testing, ophthalmic optics.