Towards a uniform specification of light therapy devices for the treatment of affective disorders and use for non-image forming effects: Radiant flux.

BACKGROUND: For treating affective disorders like SAD, light therapy is used although the underlying mechanism explaining this success remains unclear. To accelerate the research on defining the light characteristics responsible for inducing a specific effect a uniform manner for specifying the irradiance at the eye should be defined. This allows a genuine comparison between light-affect studies. An important factor impacting the irradiance at the eye are the radiant characteristics of the used light therapy device. METHOD: In this study the radiant fluxes of five different light therapy devices were measured. The values were weighted against the spectral sensitivity of the five photopigments present in the human eye. A measurement was taken every five minutes to control for a potential stabilizing effect. RESULTS: The results show that all five devices show large differences in radiant flux. The devices equipped with blue LED lights have a much lower spectral radiant flux than the devices equipped with a fluorescent light source or a white LED. The devices with fluorescent lamps needed 30 min to stabilize to a constant radiant flux. LIMITATIONS: In this study only five devices were measured. Radiant flux is just the first step to identify uniform specifications for light therapy devices. CONCLUSIONS: It is recommended to provide all five α-opic radiant fluxes. Preferably, the devices should come with a spectral power distribution of the radiant flux. For the devices equipped with a fluorescent lamp it is recommended to provide information on the stabilization time.

Recommendations for measuring non-image-forming effects of light: A practical method to apply on cognitive impaired and unaffected participants.

BACKGROUND: The non-image-forming effects of luminous radiation on people with intellectual disabilities or dementia received attention from researchers. Such studies, however, have generally been conducted using disparate methodologies which precludes generalization and reproducibility. OBJECTIVE: The aim of this study was to determine the practical applicability of measurement devices for studies investigating non-image-forming effects of luminous radiation, specifically for people with intellectual disabilities or dementia. METHODS: In three experiments, ten cognitive impaired people and thirty-nine unaffected subjects participated by wearing one or more portable devices. Six devices were assessed in total. Measurement data was accompanied with user experiences obtained from questionnaires, interviews and observations in order to assess the devices on practical and comfort issues. RESULTS: On average, the devices worn by the cognitive impaired subjects were not experienced as annoying or irritating. No significant differences are found between genders and for one of the portable devices significantly less annoyance was reported by the cognitive impaired participants compared to the unaffected group of participants. INNOVATIVE SOLUTION: The three phases of the research process in towards measuring personal luminous exposures are: selection of the most suitable portable device, application of the assessment method, and the application of the device in the (pilot) study. CONCLUSIONS: However, the findings of this study suggest that inaccuracies potentially caused by practical and comfort issues associated with the portable devices need to be considered.