Technical Lighting Help

Non-Visual Photoreceptors

What the heck are non-visual photoreceptors and why do I care about them? I’m not a research scientist, so let me explain this in the way I understand it. Please don’t use this simplified explanation in your application for a Nobel Prize!

Photo by Dih Andru00e9a on

When I started to research the color of light and its impact on human health, perhaps ten years ago, I became aware of the circadian cycle built into the human body (and almost every animal.) Our understanding of the circadian rhythm is actually new science. It was first realized in 2000. At the time, we began to learn about non-visual receptors in our eyes (iPRGC) whose singular job is to detect levels of blue light, thereby turning on and off the body’s production of melatonin, which in turn drives our circadian. More recently, scientists have learned that there are other factors that control this important body-clock.

An educational session at LightFair 2021 talked about new research that has uncovered additional non-visual photoreceptors that help our body function, based on the color of light with which they interface.

In a previous post, (Baseball and Lighting) I reminded readers that our body was engineered with only natural light in mind. The body needs blue light during the day and darkness at night. Unfortunately, we have chosen, over the last 100 years or so to live in opposition to the natural environment, employing artificial light. That artificial light presents to our body wavelengths different than the sun’s and different than what we need, hence the health problems we are encountering.

Melanopsin regulates the circadian with input from the iPRGC in the eye. New research indicates we have other “light sensing proteins,” opsins that have their own specific demand for light and their own specific reason for needing it. Because artificial light does not now deliver that type of wavelength, adverse medical conditions are occurring. Opsin 5, Neuropsin is located in the brain, skin, retina and cornea. Opsin 4, Encephalopsin is found in the brain, skin, retina and fat cells. That means there are tissues in our body that are light sensitive.

It is believed that a reduction of the light anticipated by these opsins is responsible for elevated retinopathy in infants, increases in myopia and the regulation of metabolism. Most every lighting system used today is designed, understandably, for the body’s visual system. In the future, we will likely need to design and employ systems that address the needed wavelengths of light by these opsins.

How Will This Be Done?

Again, we should remember the sun. The sun delivers light at every wavelength, in varying values. By looking at the research and the levels of light required, engineers can create artificial light commensurate with the needs of our visual system AND our non-visual receptors.

The direction in which light reaches us is also important. As you know, most artificial light comes to us from overhead, but the sun travels through the sky in an ever-changing pattern starting very low in the morning, overhead at midday and again, near the opposite horizon in the evening. That means our bodies anticipate more vertical light than we currently receive. We should expect this solution to come in fewer ceiling flush lights, more task plane lighting and even illuminated walls and panels.

At this point, there are some products on the market that address this need. As the research continues and grows, expect to see and hear more. Just remember, like so much in lighting lately, change is afoot!

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