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The Science Behind Light

Los humanos evolucionaron en la Tierra durante miles de años antes de la invención de la luz artificial en condiciones de luz natural de la luz solar, la luz de la luna y un poco de luz de fuego. Estas condiciones de luz natural se reflejan en la estructura física del ojo, y los conos se ajustan a la luz del día y a las condiciones de luz de las barras durante la noche. Hay otra forma de sensor de luz en el ojo descubierta más recientemente que no contribuye directamente a la vista pero que juega un papel en la secreción de melatonina: las células ganglionares de la retina intrínsecamente fotosensibles (ipRGC). Los humanos son seres diurnos (durante el día), mientras que otros animales son nocturnos, por lo que nuestro patrón normal de vigilia y actividad es durante el día.

Durante los últimos diez años, los científicos del cerebro han descubierto que, además de los patrones de luz que se transmiten a través del nervio óptico al centro visual del cerebro, también hay una rama que transmite datos sobre las condiciones de luz a un centro de comando en el cerebro llamado El núcleo supraquiasmático (SCN).

The SCN processes the light data and sends command signals to several glands in the endocrine system toconceptual-diagram-of-suprachlasmatic-nucleus
either secrete or suppress secretion of certain hormones critical to normal body function. The pineal gland, in the hypothalamus in the brain, suppresses secretion of melatonin in the presence of bright white light, specifically when the SCN has identified a narrow 10 nanometer band of light spectrum (out of 330 nanometers of human visible light spectrum) from 450 to 480 nanometers. When melatonin secretion is suppressed we become more alert. Melatonin secretion normally occurs when exposure to the bright white light diminishes, e.g. at sundown, but only does so if the trigger has been set by bright white light exposure earlier in the day. Melatonin also serves as a powerful antioxidant which floods the body with natural anti-cancer agents while we sleep.1

The adrenal gland is also largely controlled by the SCN based on light conditions in an opposite way from melatonin. Cortisol secretion is stimulated in the presence of bright white light and suppressed normally at night. Cortisol serves as a wakeup call to the body, raising our core body temperature, heart rate, and blood pressure from a sleep state, and is also a factor in normal digestion. If the SCN does not signal the adrenal gland to secrete cortisol, we may be tired and listless. Changes in our digestive system could cause abnormal processing of foods especially carbohydrates and can be a factor in hypoglycemia associated with diabetes.3

People that lack exposure to natural sunlight are the most prone to have issues with mental and physical well-being resulting from abnormal hormonal secretion. The result can be sleep deprivation and the many issues that accompany it, including depression and circulatory issues, among others.


Unfortunately, traditional lighting does not provide the specific spectrum of light required between 450 and 480 nanometers for normal secretion and suppression of melatonin. Even with specialized “natural” light fluorescent tubes the required light spectrum is at a low point in providing the critical spectrum while there are peaks on either side of the narrow band. The problem of proper light exposure cannot be solved by simply increasing the level of fluorescent light.





Fortunately, LED lighting is far more controllable in terms of light spectrum as well as in terms of dimming and low glare if well designed. Light being emitted from a source can be measured in spectral power density (SPD) at specific light spectrums measured in nanometers. LEDs used in the WalaLight fixtures have a perfect score of 100% SPD at the desired light spectrum as suggested by leading brain scientist. This is important, as the critical light spectrum can be passively delivered at reasonable levels of light in the ambient environment. Previously, light therapy devices required a patient actively to stare into a bright light box for two hours – which is an unpleasant experience to say the least – and not something many people can be expected to do. Delivery of the needed light spectrum passively will help assure all occupants receive the desirable light and do not require active therapy.

The WalaLights are designed as a side-lit LED panels, the light is indirect light and a pleasant glow to the eye, even at the higher light levels recommended by the Illuminating Engineering Society (IES) for various types of spaces (senior living, schools, office buildings and much more). With traditional lighting, it is very difficult to even achieve the recommended light levels in a tolerable manner, and impossible to provide the critical light spectrum for circadian light. Assuring that the occupants have adequate light levels to enjoy their tasks, work and hobbies, will raise their activity levels and mental engagement.

There is a second part to the required light. While it is critical to have the bright white light especially in the spectral-power-density-led-2morning, it is equally important to have warmer light with less blue light later in the afternoon and in the evening. If there is only bright white later in the day, melatonin secretion will continue to be suppressed.

The WalaLightTM Healthy LED Lighting System lends itself to control so with modern wireless radio frequency control systems such as ZigBee, which is an IEEE telecommunication standard widely deployed by electrical power utilities to communicate wirelessly with smart meters and appliance among others, that facilitates implementation of automated lighting controls on a facility-wide basis for such functions as circadian light scheduling. The WalaLights use both bright white and warm diodes, making it possible to control the light so the bright white is provided in the morning when needed and the warm light later in the day. This is similar to how the light from the sun changes as the evening arrives. The lighting system can also be linked through ZigBee to other automated sensor and control systems, such as fire detection and security systems.

In addition to the host of wellness benefits described above, WalaLights can deliver up to 85% reduction in electricity consumption as well as providing maintenance-free lighting for up to 100,000 hours. For a light fixture on 24 hours per day, such as in a hallway, 100,000 hours of operation equals approximately 12 years. Light bulb maintenance is a significant component of facility maintenance and can free-up valuable employees to perform other maintenance tasks.

Author: Rodney Smith, Chief Technology Officer


1 The American Cancer Society
2 Brainard, G.C. et al, Action Spectrum for Melatonin Regulation in Humans: Evidence for a Novel Circadian Photoreceptor, Journal of Neuroscience 21 (2001) 16, pp 6405-6412.
3 The Cortisol Awakening Response-applications and implications for sleep medicine, G.J. Elder, M.A.
Wetherell, N.L. Barclay, J.G. Ellis, Sleep Medicine Review 2014 June; 18(3):215-24.

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