According to Lux Magazine:

Neuroscientist professor Russell Foster…led the team at Oxford University which discovered the eye’s third photosensitive cells, creating a whole new paradigm in interior lighting.

Previously unknown to science, the cells hold the key to our understanding of our body clock, and how light affects us in profound ways, and discoveries of this type are creating a whole new genre called circadian lighting.

The finding 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.

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 the cells discovered by Foster’s team 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 and wake pattern.

The lighting industry is starting to respond with so-called ‘human-centric’ or ‘circadian’ lighting, dynamic lighting systems which mimic the changing colour and intensity of daylight in building interiors.