Commercially Available Phototherapy Devices for Treatment of Depression: Physical Characteristics of Emitted Light.
Level 5 - mechanism / opinion, no new human data
Bench laboratory testing of medical/commercial devices without human clinical data (level assigned by design analogy)
PubMed 36101875 · doi:10.1176/appi.prcp.2019.20180011
What was done
Researchers tested 24 commercially available light therapy devices provided by 12 manufacturers (16 light boxes, 1 light column, 4 LED beam devices, and 3 light visors). Physical properties were measured, including spectral power distribution, light dispersion, glare discomfort, adequacy of diffusion, photopic illuminance (lux), melanopic illuminance relative to photopic illuminance (efficacy ratio), and blue light hazard relative to melanopic illuminance (protection ratio). Performance was evaluated against clinical criteria requiring adequate light delivery at a reasonable distance, over a reasonable field of illumination, and with user acceptability.
What was found
Physical properties of emitted light varied widely across devices. Only 7 of the 24 devices (all larger light boxes) met all three clinical criteria. Multiple devices marketed as 10,000-lux units achieved this output only at unreasonably close distances, across a restricted field, or with unacceptable glare or uneven illumination. Five additional devices emitted light with physical profiles less supported by clinical evidence.
Why it matters
Many commercially sold light therapy devices fail to provide clinically adequate or comfortable light doses under realistic conditions despite marketing claims. Clinicians and patients cannot rely solely on commercial labeling when selecting light boxes for depression.
Limits
The investigation was a bench physical measurement study and did not evaluate clinical patient outcomes. The sample was restricted to 24 loaned or donated devices and may not reflect the full commercial market. Specific numerical metrics for illuminance, distance, and spectral ratios were not reported in the abstract.
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