1、 Standard positioning and version
ISO 15004-2 is an international standard entitled "Basic Requirements and Test Methods for Ophthalmic Instruments Part 2: Protection against Light Hazards", which specifies the classification, terminology, exposure limits (covering the 250-2500 nm wavelength band), measurement and test methods, and manufacturer warning information requirements for the safety of ophthalmic instruments from light radiation. The current version is ISO 15004-2:2024 (second edition, released on December 5, 2024), which has replaced and abolished the 2007 version. For myopia prevention and control devices (especially products that use PBM-LED red light irradiation), this standard is the core basis for proving the safety of photobiology. Similar domestic testing will also be carried out in conjunction with YY/T 0065, GB/T 20145-2006, YY 9706.257-2021, YY/T 1534-2017 and other standards.
2、 Instrument classification (Group 1/Group 2)
The standard divides ophthalmic instruments into two categories based on the risk of light radiation. Group 1 is an instrument with no potential optical hazards, and its radiation output does not exceed the limit specified by the standard; Group 2 is an instrument that emits radiation exceeding the limit of Group 1 and requires a more rigorous evaluation with accompanying usage restrictions. For myopia prevention and control devices, mainstream red light products rely on being recognized as Group 1 (Class 1 instruments) through testing as a safety selling point - for example, some products claim that the light irradiation intensity is only 10% of the international safety limit, with a safety redundancy of up to 10 times.
3、 Hazard types and assessment bands
The testing focuses on three main types of photobiohazards: assessing the risk of acute burns and chronic damage to the cornea and lens in the ultraviolet band (approximately 250-400 nm); Assessment of retinal photochemical damage (blue light hazard) in the visible and blue light bands (approximately 300-700 nm); Evaluate the risk of thermal burns to the cornea and fundus in the near-infrared band (approximately 760-2500 nm).
4、 Core measurement parameters
The key parameters that the testing system needs to measure include: spectral distribution of the light source, corneal irradiance, retinal irradiance, radiance, apparent light source angle α, retinal image size dr, as well as pulse energy and pulse waveform of the pulse light source. When measuring, the spectral data is multiplied by the standard bioweighting function and integrated to obtain a weighted radiation value, which is then compared with the limit value: A (λ) weighting is used for retinal photochemical hazards (sum range 305-700 nm), and R (λ) weighting is used for visible/infrared retinal thermal hazards (sum range 380-1400 nm). For example, in the 2007 version, the limit for photochemical hazards of the retina is weighted irradiance not exceeding 0.22 mW/cm ², and the limit for thermal hazards is 350 mW/cm ².
5、 Test conditions and type of light source
The test needs to cover the continuous and pulse working modes of the instrument separately, and adopt the most unfavorable usage conditions (such as closest eye distance and maximum output gear). The complete optical performance test of a single device can usually be completed in about 20 minutes. For scenes where multiple light sources are stacked (such as simultaneous output of treatment light and aiming light), the 2024 version requires the use of radiation stacking algorithm to calculate the comprehensive hazard.
6、 New requirements for ISO 15004-2:2024
The important changes in the 2024 version compared to the 2007 version include: introducing the Recommended Maximum Exposure Value (RME) for Group 2 instruments, specifying the allowed cumulative radiation dose, maximum safe exposure time, and maximum number of pulses for each mode; Clearly stating that exceeding the limit will result in irreversible eye damage; The safe calculation of beam movement rate should be considered for scanning light sources; The automatic cut-off trigger threshold for the time limited protection device is required to not exceed 90% of the RME; After the detachable filter fails, the overall radiation of the machine must fall back to the range of Group 1.
7、 The practical significance of myopia prevention and control devices
The red light myopia prevention and control device (commonly in the 630-660 nm wavelength range) is used to directly irradiate the fundus for a long time, and its safety controversy is focused on retinal thermal and photochemical damage. Therefore, ISO 15004-2 testing is a key evidence for registration and application (such as domestic Class II medical devices) and building parental trust. The common practice in the industry also includes engineering protection such as avoiding the macular fovea through optical path design, controlling single dose, built-in power monitoring and timed shutdown to retain greater redundancy within safety limits.
8、 Summary
The essence of ISO 15004-2 testing is to measure the spectral and radiation parameters of the instrument output under the most unfavorable usage conditions, and compare them with the standard exposure limit after bioweighting, thus completing the Group 1/Group 2 classification. For manufacturers of myopia prevention and control devices, the goal is usually to ensure that the product remains stable in the Group 1 category in all operating modes, and to meet the additional requirements of the 2024 version for protective mechanisms through design such as dose locking and automatic shutdown.
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