Red light instruments for myopia exceed safety limits.

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Photobiology

Background:

• Low-level red light (LLRL) therapy is an emerging treatment for childhood myopia.
• Previous studies suggest LLRL effectively reduces axial elongation and myopia progression.
• The safety parameters of LLRL devices for pediatric myopia control require thorough investigation.

Purpose of the Study:

• To characterize the optical output of two LLRL devices used for myopia control.
• To determine the maximum permissible exposure (MPE) limits for thermal and photochemical damage from these devices.
• To assess the safety of LLRL therapy for children with myopia.

Main Methods:

• Two LLRL devices (Sky-n1201a, Future Vision) were analyzed.
• Optical power was measured using an integrating sphere radiometer following ANSI standards.
• Retinal spot sizes were determined using a model eye and beam profiler; corneal/retinal irradiance and MPE were calculated.

Main Results:

• Both devices were classified as Class 1 laser products.
• Sky-n1201a: 654-nm wavelength, 0.2 mW power, 7.2 W/cm² retinal irradiance.
• Future Vision: 652-nm wavelength, 0.06 mW power, 0.08 W/cm² retinal irradiance.
• For both devices, 3 minutes of viewing approached or exceeded MPE limits for retinal damage.

Conclusions:

• Continuous viewing of evaluated LLRL devices for 3 minutes risks photochemical and thermal retinal damage.
• Clinicians must exercise caution when using LLRL therapy for pediatric myopia.
• Further research is needed to establish definitive safety standards for LLRL myopia control.