Light: the basis of life
As is the case with all other living beings, light is indispensible to our health and well being. Whether it is due to seasonal or socio-economic factors, the amount of light we receive may prove to be inadequate. It is estimated that 10 to 20% of the population suffers from mild light deprivation, while between 5 and 10% suffer from major light deprivation. As a result, some people have a tendency to depress and/or some sleep disorders. When we don’t get enough light from nature, light therapy is the alternative that can supply the light we need.
Light therapy is a medical treatment that consists of exposing the eyes to light of a specific intensity and visible spectrum that is close to sunlight every day for a given length of time depending on the indication.The beneficial effect of light is linked to its physiological action particularly its influence on secretion of melatonin, the “sleep hormone,” and serotonin, a neurotransmitter.
How does light work?
In general, light stops the secretion of melatonin, also called the “sleep hormone,” which facilitates waking up in the morning, supplies energy, and ensures alertness throughout the day.
More specifically, light stimulates photoreceptors present in the lower part of the retina, which then activate the part of the brain that controls our biological clocks. In turn the biological clock sends the order to stop the secretion of melatonin.
How intense?
The light intensity of a lamp is expressed in lux and corresponds to the intensity of light received by the eye at a given distance from the lamp. The minimum intensity depends on the light spectrum and the length of exposure.
For a white-light lamp, and a thirty-minute treatment, 10,000 lux (generally at a distance of 30 cm) is necessary.
For a blue-tinted lamp and a 30-minute treatment, 2,000 lux have the same effectiveness for extra comfort.
White light or blue light?
It has been scientifically proven that the wavelength of blue (+- 470 nm) is responsible for stopping the secretion of melatonin.
In the last few years, concern has arisen regarding the use of high brightness blue LEDs. The studies in question examined the use of very high-intensity LEDs (>50,000 lux) under long-term working conditions (8 hours). Unless studied otherwise, LED light therapy lamps emitting white light with an intensity of 10,000 or fewer lux were not part of these studies.
*Glickman-Byrne – Pineda – Hauck – Brainard in Biological Psychiatry, 59 (6), 15 mars 2006, pp 502-7
How long does a session last?
It all depends on the light intensity and the distance between your eyes and the lamp. A 10,000 –lux dose of white light for 30 minutes has a similar effect to a 2,000-lux dose for two hours.
With the Luminette®, the distance between the light source and the reception zone, the retina, is reduced. This allowed the Luminette®’s designers to reduce the light intensity, and thus the glare, considerably, while conserving maximum efficiency.
Treatment at what time?
The time of day when the patient is exposed to the light plays an essential role in the effectiveness of the treatment. An exposure to light at noon has little effect. An application in the evening makes the patient fall asleep later, while an application in the morning will make the patient fall asleep earlier.
The time of exposure depends on the indications for light therapy:
- Winter depression: As early as possible after waking up.
- Sleep disorders due to phase lag: As early as possible after waking up.
- Sleep disorders due to phase lead: Late afternoon/early evening
- Extended night shift work: As close as possible to the start of the night shift
Témoignage de Jean-François Bouveret
