ISO 18526-1:2020

Overview

ISO 18526-1:2020 - "Eye and face protection - Test methods - Part 1: Geometrical optical properties" defines reference test methods for measuring the geometrical optical properties of nominally plano (non‑corrective) lenses used in eye and face protectors. The standard specifies procedures to determine spherical, cylindrical and prismatic refractive power for both unmounted and mounted lenses, including calibration and uncertainty requirements for test apparatus. It is a reference method; alternative methods are permitted only if demonstrated to be equivalent and to meet the same measurement uncertainty.

Key topics and technical requirements

• Scope and applicability: Applies to plano lenses for eye and face protection. Not intended where other product requirement standards specify different test methods.
• Test methods covered:
  • Telescope method for spherical and cylindrical refractive power and prismatic power (6.1).
  • Prism imbalance measurement for complete protectors or lenses covering both eyes (6.2).
  • Tests for spatial deviations and evaluation of image aberrations (6.3).
• Apparatus and setup:
  • Telescope with reticule (nominal 20 mm aperture; magnification ×10–×30) and an illuminated target with specified pattern and dimensions.
  • Optional spectral filter to reduce chromatic aberration; controlled light source.
  • Typical telescope–target distance specified (4.60 ± 0.02 m) and detailed target geometry.
• Calibration and uncertainty:
  • Apparatus calibration to achieve measurement uncertainty ≤ 0.01 D (dioptre) for refractive power (Annex B describes a variable‑distance calibration method).
  • Prism imbalance uncertainty ≤ 0.05 Δ (prism dioptre).
  • Annex A provides application of the uncertainty of measurement (reference to ISO/IEC Guide 98‑3 / GUM).
• General test conditions:
  • Tests performed by trained observers, using reference points defined in ISO 4007.
  • Ambient temperature and humidity guidance and sample preparation rules are included.

Practical applications and who uses this standard

• Manufacturers of safety eyewear and face shields for verifying optical quality of plano lenses.
• Accredited testing laboratories performing compliance and quality control testing for personal protective equipment (PPE).
• Procurement and QA teams in industries (construction, manufacturing, healthcare) that require validated optical performance of protective eyewear.
• Standards bodies and conformity assessors assessing measurement traceability, calibration, and uncertainty.
• Design engineers and product developers using precise refractive and prismatic specifications to reduce distortion and ensure wearer safety.

Related standards

• ISO 18526 series (other parts), including ISO 18526-2 and ISO 18526-4 (headforms)
• ISO 16321 series (requirements for occupational eye and face protectors)
• ISO 4007 (vocabulary for eye and face protection)
• ISO/IEC Guide 98‑3 (GUM: uncertainty of measurement)
• ISO 18527 (sports eye protectors) and ISO 19734 (selection/use guidance - under preparation)

Keywords: ISO 18526-1:2020, eye and face protection, geometrical optical properties, refractive power testing, prismatic power, plano lenses, telescope method, PPE optical testing.