Beyond Vision: Light's Effectiveness in Eliciting Human Responses

Price, Luke Llewelyn Anthony (2020). Beyond Vision: Light's Effectiveness in Eliciting Human Responses. PhD thesis The Open University.



Optical radiation affects health via diverse and interconnected mechanisms. The skin and eyes support multiple actinic processes, exploiting environmental optical radiation, including light, to the benefit of the whole body. Sub�optimal exposures can disrupt these processes and in extreme scenarios may cause tissue damage. Natural and artificial lighting can lead to both beneficial and unwanted responses; understanding how to achieve a healthy balance relies on quantitative exposure data and dose�response relationships based on physical measurements.

Through non-visual retinal photoreception, light has a profound effect on daily patterns of human physiology and behaviour. This thesis reviews the spectral weighting function, action spectrum, for the regulation of plasma melatonin, and its relation to photoreceptors, melanopsin, circadian rhythms, standardisation, health advice and eye safety.

In my portfolio, I have contributed to understanding human non�visual responses to light. The human photoreceptor calculation tool I constructed is widely used and supports an International Standard. I published a revised circadian light�drive model based on melanopsin photoreception, and coordinated multidisciplinary advice on shift work health studies.

Short-wavelength light synchronises day and night time activities with the environment. Bright artificial light at night can interfere with this process, and high radiance blue light can cause retinal lesions. I have contributed practical advice on the efficacy of bright light therapy products, confirmed the eye safety of display screens, and raised concerns about the modulation or flicker from some LED lighting.

My published advice is based on field measurements of human exposures to light and experience gained of gathering exposure data. In the final section of my portfolio, my work has included characterising the performance and use of wearable broadband dosimeters and light-weight CCD array spectroradiometers, proposing performance requirements for wearable sensors and developing the closest�matching melanopic light�logger from an existing product

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