calendarSep 17. 2022
clock Reading time: 6 minutes

Melanopic effectiveness: Why light affects us not only visually

Natural daylight has a positive effect on our health - this fact has already spread. But it is non-visual aspects that control our biorhythm. In this article you will find out exactly what happens in our eyes and which factors play a role in enabling us to achieve similar effects indoors using artificial light.

What is the melanopic efficacy of light?

It is probably well known that light has a visual and an emotional effect on us. For example, we need bright and high-contrast lighting for good vision (visual effect), while suitable light colors ensure a pleasant lighting mood (emotional effect).

So far, however, the biological effect of light is probably largely unknown: the so-called melanopic effectiveness. Why "melanopic"? This name comes from the hormone melanopsin and is the hormone that makes us sleepy. Because the appropriate light either suppresses the melanopsin and thus activates our body - for higher concentration and performance. Or the melanopsin is not suppressed and begins to relax our bodily functions and prepare us for a restful sleep. This process of melanopsin stimulation or suppression is called the melanopic or biological light effect.

This biological, non-visual effectiveness of light is therefore directly related to our biorhythm (or: sleep-wake rhythm). Short-term effects of a melanopsin suppression are alertness and a high ability to concentrate - a long-term effect of a melanopsin level adapted to the natural course of daylight is an overall healthy sleep-wake cycle.

more about the biorhythm

A groundbreaking discovery: the retinal ganglion cells of the eye

Research into so-called chronobiology, i.e. the biology of natural body cycles, began around the second half of the 2th century. It is even shorter since researchers discovered light-sensitive ganglion cells on the human retina. These are the receptors in the eye that exclusively process the non-visual, biological stimuli of light: the intrinsically photosensitive retinal ganglion cells (ipRGC). In contrast to this, the other previously known receptors in the eye are used purely for the visual process: the approx. 20 million rods for twilight vision (scotopic vision) and the approx. 120 million cones for daytime vision (photopic vision).

Only with the discovery and further research of the retinal ganglion cells was the missing piece of the puzzle available to properly understand the human circadian rhythm. Finally, in 2007, it became apparent that the active substance melanopsin in the retinal ganglion cells is responsible for this rhythm and which factors activate or suppress the release of this hormone.

Melanopic Efficacy – Factor 1:The temporal structure of light

Our circadian rhythm evolved as humans evolved in the light of the sun. Our natural sleep-wake rhythm still works today - as it did with the first Homo Sapiens - according to the same principle: from sunrise to midday sun to sunset, every time of day has different light intensities and color temperatures. Exactly this dynamic must therefore also be reproduced in an artificial light control system so that we do not lose our rhythm in terms of health.

Melanopic effectiveness – factor 2: The meaning of different color temperatures

Depending on the wavelength and thus the color temperature of the light, the light falling on our eyes has a different biological effect. This connection is described in chronobiology as a melanopic effect factor. This is a measure of the influence of a light source on our biorhythm. A high proportion of blue in the light ensures a reduced release of melanopsin and thus concentration and performance, while a high proportion of red increases the release of melanopsin and ensures relaxation.

Melanopic effectiveness – factor 3: The angle of incidence of the light:

Since the retinal ganglion cells are mainly located in the lower, rear area of ​​the retina, they can logically only be reached particularly well with a certain angle of incidence of light. This is between 0-45° (relative to the horizontal). This corresponds to the field of vision in which we also perceive the daylight of the sun.

Melanopic effectiveness – factor 4: The flatness of the light

This also makes it clear why large areas in particular achieve particularly good biological effectiveness - in line with the natural sky. These can either be large illuminated areas (such as a luminous ceiling or luminous tiles) or room surfaces (walls or ceilings) that are illuminated. Both ensure a flat luminance, if possible in the visual range of 0-45° and an intensity between 500 - 1000 cd/m². If the luminance rises above this value, the luminous surface can lead to glare.

Melanopic effectiveness – factor 5: our age

With increasing age, not so much light can fall on the receptors through the smaller pupils and eyes that are already clouded. That is why older people need more light than younger people to achieve the same melanopic effect. For this reason, there are two correction factors for the melanopic effect factor that show: In contrast to a 20-year-old, a 60-year-old needs almost four times more light to achieve the same biological effect in the eye.

Human Centric Lighting: Why dynamic lighting control is good for our health

An exact simulation of the natural course of daylight with the high illuminance of sunlight is hardly possible with artificial light, but dynamic lighting control can trigger important, non-visual influences. For this, the previously mentioned factors, which determine the melanopic effectiveness, should be integrated as well as possible into a lighting plan.

That means: the right light at the right time, with the right intensity and the right color temperature at the right angle of incidence.

Biologically effective light in the home office

At first glance, this sounds like a tricky task. With the right light in the home office, you can already set important biological impulses.

An example is ours Table lamp Helios AV: With Helios – at the highest level – lighting values ​​are achieved that have the same effect as 10.000 lux strong sunlight. In the pre-programmed course of daylight, the most important values ​​are already set in both lights: namely the right color temperatures (2.000 to 6.500 Kelvin) and light intensities for the respective time of day, and with the right melanopic effect factor and the right light incidence angle (from the front above), without any glare or Flicker.

With our smart office lights, there is a melanopic lighting effect in the home office throughout the day - simply at the touch of a button.