Overview
ISO 22665:2012 specifies minimum requirements, test methods and verification procedures for instruments and systems that measure the axial length of the human eye. It covers both ultrasound biometry (contact and immersion modes) and optical biometry (e.g., partial coherence interferometry), defines the axial length reference (anterior corneal surface to ILM or RPE), and addresses conformity checks to ensure reliable ocular distance measurements used in intraocular lens (IOL) power calculations.
Key topics and requirements
- Scope and definitions: Clear terms such as axial length, phakic/aphakic modes, contact/immersion ultrasound, optical biometry and group refractive index.
- Performance tolerance: Measured radial and axial dimensions of test bodies must lie within ±100 µm of the true dimensions.
- Test methods:
- Use of standardized test cylinders (Annex A), typically PMMA, representing small/medium/large eyes.
- For ultrasound: perform both contact and immersion measurements; instruments set to aphakic mode for testing.
- For optical biometry: operate in a mode that yields optical path length and convert to geometrical distance using the temperature-corrected group refractive index.
- Ten independent measurements per orientation (axial and radial) are taken and averaged; each measurement must be re‑adjusted to be independent.
- Calibration and temperature corrections:
- True dimensions determined with mechanical callipers (accuracy ≤ 10 µm).
- Temperature-dependent corrections for sound velocity (ultrasound) and group refractive index (optical) are mandatory.
- Documentation and marking:
- Instruments must include instructions for use, disinfection procedures, manufacturer details and a reference to ISO 22665 when claimed compliant.
- Permanent marking: manufacturer name/address, model, serial number, and IEC 60601‑1 required markings.
Applications and users
ISO 22665:2012 is directly applicable to:
- Manufacturers of ophthalmic biometers (ultrasound and optical) for device design, validation and regulatory submissions.
- Calibration and test laboratories performing conformity testing and device verification.
- Clinical engineers and hospital ophthalmology departments that validate and compare axial length measurements for cataract and refractive surgery planning.
- Regulatory bodies and notified bodies assessing compliance for market approval.
Practical benefits include improved measurement comparability between devices, more reliable IOL power calculations, and standard procedures for device evaluation.
Related standards
- IEC 60601-1 - Medical electrical equipment: general safety and essential performance (normative reference in ISO 22665).
- ISO 22665:2012 prepared by ISO/TC 172 (Ophthalmic optics and instruments).
Open preview (PDF)Ophthalmic optics and instruments - Instruments to measure axial distances in the eye
