Overview
EN ISO 10938:2016 - Ophthalmic optics: Chart displays for visual acuity measurement (printed, projected and electronic) specifies standardized characteristics for visual-acuity chart displays used in general clinical practice. It covers optotypes produced by chart projectors, electronic displays and printed media (opaque or transilluminated) where recognition of high‑contrast optotypes is used to measure visual acuity.
Key topics and technical requirements
- Optotype definition and sizing
- Optotype sizes are specified by the size of their critical detail (e.g., the Landolt ring gap).
- Permissible size deviation: ±5% for critical detail.
- Luminance and uniformity
- Background luminance shall be between 80 cd/m² and 320 cd/m² (manufacturer to specify); recommended 200 cd/m².
- Luminance variation shall not exceed 30% within two character diameters of an optotype, and 50% across the entire illuminated field.
- Contrast and quality of presentation
- High-contrast optotypes are required; the standard addresses contrast, presentation quality and legibility considerations.
- Resolution and critical detail
- Resolution is defined as the smallest separation at which two lines are distinguished.
- Requirements cover optical resolution for projected charts and pixel/sample resolution for electronic displays.
- Requirements specific to media
- Optical projection: focus range, projector screens and projection-specific performance.
- Printed charts: material, transillumination considerations and stability of optotype size and contrast.
- Conformity, testing and documentation
- Type-test and conformity procedures, resolution tests, required accompanying documents, marking, labelling and packaging.
- References conformity to ISO 15004-1 (fundamental requirements for ophthalmic instruments).
Applications and who uses this standard
- Eye care professionals and clinics - to ensure clinical visual acuity tests are consistent and repeatable across printed, projected and electronic charts.
- Manufacturers and designers of chart projectors, electronic acuity displays, backlit or printed charts - to design products that meet standardized size, luminance, contrast and resolution criteria.
- Test laboratories and conformity assessors - to perform type tests, resolution and luminance uniformity checks.
- Regulatory bodies and procurement - to specify compliant visual-acuity measurement devices in tenders and approval processes.
Related standards
- ISO 8596 - Standard optotype and presentation (reference for Landolt ring and optotype arrangement).
- ISO 15004-1 - Fundamental requirements and test methods for ophthalmic instruments.
Keywords: EN ISO 10938:2016, ophthalmic optics, visual acuity measurement, optotypes, Landolt ring, chart projectors, electronic charts, luminance, contrast, resolution.
