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Meet the godfather of circadian lighting

Surprisingly, the ganglion cells were only discovered relatively recently – in 1991 – by an Oxford University team led by the neuroscientist Russell Foster.

Neuroscientist – and keynote speaker at next month’s lightspace dot london event – Russell Foster led the pioneering team at Oxford University which discovered the eye’s third photosensitive cells, creating a whole new paradigm in interior lighting. Ray Molony reports. 

Circadian rhythms describe patterns of behaviour that exist in most things that live on this planet of ours. 

It’s not just the higher mammals that exhibit these patterns, you’ll find it in most organisms, from plants and animals all the way down to microbes. However, we are the only species that makes a habit of living in ways that disturb our natural balance with the world around us.

The discovery of the ganglion cells in the eye has led to the creation of so-called ‘circadian lighting’, where light works in harmony with occupants’ natural rhythms. The lighting industry is starting to respond with innovations such as the Coelux artificial skylight, which can be seen on stand C42 at lightspace dot london.

Circadian comes from the Latin ‘circa, meaning’ ‘about’ and ‘dies’ meaning ‘day’. So, a circadian rhythm is a repeating pattern based on the natural progression of night and day.

The obvious example of a circadian rhythm is our decision to sleep when it’s dark and be active during the day. On one level it’s just the practical thing to do, given that most of us require illumination to function, so darkness serves us well as the time to rest. But there’s a chemical response going on as well.

During the day, the eye gathers light information, in particular the amount of blue light that is present in the environment. Most of us know about the rods and cones that govern the visible side of things, but recently another group of cells has been found within the eye. These are called, unpromisingly, the intrinsically photosensitive retinal ganglion cells and are sensitive to a narrow range of blue light, around 480nm, and it’s these that are key to controlling our circadian rhythms with light.

When the amount of 480nm blue drops below a certain level, the pineal gland is instructed to secrete a hormone called melatonin, and it’s this biochemical messenger that effectively sets in train the body’s sleep pattern. 

Surprisingly, the ganglion cells were only discovered relatively recently – in 1991 – by an Oxford University team led by the neuroscientist Russell Foster.

The discovery has changed our understanding and appreciation of the power of light to affect us. In fact, some are starting to describe light as a drug, such is its power to control our health and welling as well as our circadian rhythms.

The lighting industry, unsurprisingly, has jumped on the discovery as it opens up exciting new possibilities to create lighting systems that work more in harmony with people. 

It creates a whole new market of ‘circadian lighting’ at a time when lighting products are becoming commoditised. Early systems, already installed in some schools, workplaces and care homes, feature lighting whose intensity and colour temperature change during the day, allegedly to provide benefits to occupants. 

However, the suppliers of this equipment are, understandably, coy about the specifics. The trouble is, the scientific community and the lighting industry aren’t working together on how we translate and apply the science in the real world.

Professor Russell Foster’s keynote address at lightspace dot london is, hopefully, the start of a new dialogue between scientists and lighting professionals. Don’t expect a dry, academic PowerPoint however; Foster’s a riveting presenter whose recent TED talk has been viewed over five million times.