(Full preview of Chapter 1 from "Healthy Lighting of your Homes - Guiding principles to health efficient lighting of homes". The book is available for purchase athttp://www.amazon.com/dp/B00TKSLSK4)

“ We are all connected ;

To each other biologically,

To the earth, chemically,

To the rest of the Universe, atomically”

– Neil De Grasse Tyson.

Life on earth is said to have started around 3.8 billion of years ago. Considering that earth itself came into being, around 4.6 billion years ago, we can say that “WE” have been around since the beginning of the world.

“WE” might not have been in this same shape and form that we call as humans, but many ingredients of us like, atoms, molecules, amino acids, nucleotides, RNA, DNA and proteins have been around for millions of years. They have been in the form of single cells, multiple cells and as complex cellular structures, later.

99% of our body is composed of Hydrogen, Oxygen and Carbon atoms. They combine together to form molecules, molecules combine together to form macromolecules and they combine together to form cells and so on…(Fig. 1.1)

Fig. 1.1 – Organization Structure of Life forms

We are only a conglomeration of 50 trillion cells, conjoined together to form certain organs, each performing some basic functions, efficiently.

Early forms of life on earth seem to have survived tumultuous events and harsh habitats. Earth has gone through phases, where it has been covered by trees, fire, snow and ice at different eras throughout its life. Many species have taken life and become extinct.

One constant factor, throughout our entire history of 4 billion years, has been the constant spinning and the rotation of the Earth. It meant that “WE” have always been constantly exposed to the oscillation between light and darkness, consistently for millions of years. The intelligence to actively seek and respond to light and dark cycle, is imprinted in to each and every cell of our body. Light and darkness are the fundamental energies of the universe. Everything is made up of light and everything will give off light, when excited.

At the physical level, exposure to this life giving source provided energy during the day and respite during the night. This balance of physical activity in the day to gain energy from sun only to consume the same energy during rest for maintaining our restoration and growth has been established over millions of years. Habitual activity patterns and varying proportions of light and dark exposure shaped many of our physiological and psychological traits. Being diurnal, we humans developed compact eyes with round pupil and color vision, compared to nocturnal animals, which have large eyes with slit pupil and partially or fully color blind. The intensity of the solar cycles determined our strength of happiness, alertness, cognition, moods and other behaviours. At a deeper level, our cellular batteries were charging under sunlight, in the day and draining the cellular batteries, by consuming the stored energy, in the night. As the cell batteries need light to charge itself, they need darkness to spend energy. Conversely, a charged cellular battery triggered daytime responses in our body and a drained cellular battery triggered a night time response. Even today our cells are highly dependent on this cycle for happiness, health, nourishment, effective functioning and longevity.

Light Detection

The ability to detect this light and dark cycle efficiently, by an organism, influenced its energy creation, orientation, and survival. Many organisms even developed anticipatory responses like sunflowers looking east and cortisol release in humans even before sunrise, for competitive advantage or the production of melatonin in anticipation of the onset of night for restoration, is another example of anticipatory response. The presence of light and absence of light triggered equally intensive bio chemical reactions at the cellular level, for energy capture in the daytime and energy consumption in the night time in diurnal organisms and vice versa in nocturnal organisms. Around 2 billion years ago, early life forms detected light and darkness with 3 main types of light capture molecules:

 - Chlorophyll – light to make carbohydrate photosynthesis

 - Photolyases – uses blue light to repair RNA/DNA, these are the magnetic field detectors in the retina. No longer found in humans, but not ruled out.

 - Rhodopsin – Produces chemical and electrical reactions on light stimulus and stores energy. Present in rods of human retina.

There are other types of opsins which react differently to different wavelengths of light. These opsins form the basic ingredients for the evolution of the eye and many are still active in our visual circuitry.

The present day eye is believed to have evolved over the eons. (fig 1.2). Starting as simple light sensitive pigments, they evolved in to membrane structures, then evolved basic optics which could focus and finally in to the complex eye structures that we see in insects and mammals.

Fig. 1.2 – Evolution of eye

As light sensitive pigments, it could only detect light as a signal; as membranes formed, they could sense direction; when basic optics evolved, they could form a low resolution image with depth and with the complex optics they were able to form high resolution images.

 The function of detailed vision was not there in most stages of evolution of the eye, but the function of light detection, as a signal, was there from the earliest stages of evolution of the eye, for millions of years.

Even today, our visual circuitry needs the following inputs from our visual environment,

- Light Detection

- Light Direction

- Dynamic Spectrum

- Brightness Contrasts

- Task based intensity

Starlight to Sunlight

Our eye is a marvellous piece of design, providing us with 80% of our sensory information to the brain. Crafted by a diurnal lifestyle over centuries, it helps us to see under a wide range of lighting levels from 100,000 lux to 0.01 lux. The optical system consisting of the cornea, iris, lens and ciliary muscles focus the image on to the retina.

 Fig 1.3. Anatomy of the Eye

The retina translates light in to nerve signals, distinguishes colors and provides amazing clarity to detect even specs of dust or hair few feet away.  The retina is a part of the brain which gets separated as eyes, during development of the embryo but still connected to the brain through the Optic nerve.

 The Retina has 3 layers of nerve cells, the last layer being the light sensors, the rods (R) and cones (C).

Fig 1.4 – Retinal Layers

Rods are the light sensors in the eye that help us to detect shape and motion under low lighting levels called Scotopic vision. They are about 120 million all over the retina and are absent in the centre, the area called fovea, where the fine-detail vision happens. Hence, rods help us in peripheral vision in low lighting conditions. They are highly sensitive to light, but slow in response and help us to see even under starlight.

You would have experienced this when you enter into a dark room after being in the sun, may be a noon show in a movie hall. Even though, you struggle initially to see anything, slowly, your eyes adapt to the low lighting conditions and you can see much better, once the rods adapt completely to the low lighting levels. To see even the faintest of stars, you have to look a little away from it. This way, the peripheral vision through the rods, helps us to see the faintest of starlight in low lighting levels. The moment you try to look at the star directly, it vanishes from our sight.

Rods do not work under higher lighting levels. In spite of the huge numbers of rods in our retina, clarity in peripheral vision is poor as many rods are grouped together to synapse with a large ganglion cell through the bipolar (B), horizontal (H) and amacrine (A) cells before proceeding to the retinal ganglion (G) cells (fig 1.4). So we are able to detect even the faintest of starlight but unable to achieve clarity and detail of the objects in the peripheral vision. Rods sensitivity is more towards the shorter wavelengths like blue and green under Scotopic vision (night time). You would have observed in many movies, where a simple bluish tinge is sufficient to convince us that it is a night scene. After all, moon light is nothing but reflected sunlight.

Cones are another set of light sensors in the eye that provide clarity and colors to our vision under higher lighting levels called Photopic vision. Cones are only about 6 million in number, densely packed in the fovea and sparingly spread around the retina. This densely packed fovea is where the images are focused as part of our central vision. Most of the visual field in front of us is covered by the peripheral vision. A very narrow field of vision, only 2 degree cone from the centre, called the central vision, helps us achieve visual clarity and color vision. Cones are highly responsive but low in sensitivity and help us see under varying ranges of lighting levels. Considering the same example of a noon show in a movie hall, cones help us to adapt instantly to the high intensity daylight, when we come out, even after spending 3 hours in near darkness. They do not work during low light conditions.

Unlike rods, which are grouped together before connecting to a ganglion cell, each cone in the fovea, is connected to a single ganglion cell (G), before proceeding to the optic nerve. High density of cones in the fovea and individual connection to a ganglion cell, provides us the clarity and color in Central vision. The density of cones is extremely low outside the fovea, hence the peripheral vision in the daytime, too, lacks clarity and detail. While there is only one type of rod, there are three types of cones S, M and L which are sensitive to Blue, Red and Green color wavelengths respectively. S stands for short wavelength, M for medium wavelength and L for long wavelength cone types which help us sense different wavelengths of light. M and L cones are in the fovea and the S cones are mostly outside the fovea.

When it is bright daylight, our cones are active and we have Photopic vision, when it is dim night, our rods are active and we have Scotopic vision. But, when it is neither too bright nor too dark like dusk and dawn, is when, both rods and cones are active, resulting in Mesopic vision. While rods are not active ‘visually’ during daytime, they are active ‘biologically’ playing an important role in triggering biochemical reactions signalling the onset of day or onset of night. The same is true for cones in the night. So light and darkness evoke equally strong responses from our retinal circuitry.

The middle layer of nerve cells, namely, bipolar cells (B), horizontal cells (H) and amacrine cells (A) transmit the nerve signals from the rods and cones to the front layer of ganglion cells (G) (fig 1.4), which bundle together in to an optic nerve to send signals to the brain. The circuitry is so intricate and intelligent in design that we are yet to completely understand the deeper connections. But recent research in to the light sensitive ganglion cells has provided valuable insights in to the importance of light and dark cycle and its impact on our biological functions and health.

Many of the ganglion cells in the retina are light sensitive, especially the short wavelength, which is blue light. They are spread all over the retina much like the rods but in a different layer and in relatively minimal quantities. They are extremely slower, than even rods, in response, hence need more time to adapt to the lighting levels. These special ganglion cells produce melanopsin and were discovered around the year 2001. Now, we realize that we have 3 different photo sensors, namely, rods, cones and ipRGC. Rods and cones enable vision under night and daylight conditions and ipRGC, given its extremely slow response time, probably, provides stimuli to detect the time of the day or season or onset of night or the onset of day. The discovery of these intrinsically photosensitive Retinal Ganglion Cells (ipRGC) gave a new understanding about the impact of light and dark cycle on our health. We will see more about this in the next chapter.

Light Processing

The evolutionary habit of detecting light has been triggering on or turning off important behaviours in relation to the time of the day or night. But with poor quality of information, there was no processing of information, only reflexes.

As the quantity and quality of information from these light harvesters went up, the brain evolved in parallel, to process this incessant flow of information and pass it on to the effector organs like muscles, glands, etc. Different layers of brain evolved to handle the growing size of information and the bigger need for interpretation of those information. It is thought that the brain developed out of the eye and some believe the other way. 

Fig 1.5 – Evolution of Human brain

Think of a satellite dish connection, where the eye is the dish antenna at the rooftop and the set top box is the brain. It is as though the brain is extending itself, in to the outside world for making sense of it.

For millions of years, light detection and light processing has been the fundamental function of the primitive eye and primitive brain. That is why, even today, 80% of our sensory information to the brain, is through the visual pathway, 16% through the auditory pathway and the remaining 6% is through the other senses of smell, touch and taste. Clarity and color vision were achieved much later.

The detection of light or the absence of light at the conscious level provided us with the visual cues for energy creation, physical activities, orientation and survival strategies. But more importantly, at a subconscious level, light and darkness have been regulating many of our physical activities, like waking and sleeping; biological responses like hormone secretion, body temperature regulation and many of our psychological responses like happiness, alertness, performance, emotion, mood and behaviour.

Uprooted from Nature

We have been living outdoors, predominantly, as diurnal creatures throughout our evolutionary history and our internal biological systems are used to high intensity sunlight in the day, low intensity light in the evenings and darkness in the night. With modern day lifestyle, our duration for activities are growing and rest duration is becoming shorter, our day time lighting levels have become dimmer and night time lighting levels have become brighter. This alarming disconnect from natural light and dark cycle has resulted in increasing prevalence of many lifestyle diseases and problems like, insomnia, depression, mood disorders, obesity, overeating, heart diseases, hypertension, diabetes, cancer etc. either directly or indirectly. In spite of the technological advances in artificial lighting, our day time lighting levels are static and dimmer and night time lighting levels are brighter, than what our eyes are used to. Scientists have defined this decline in day time light levels and its dynamism, as ‘Biological darkness’.  With these incorrect visual cues, our biological responses have gone awry.

We have been treating the symptoms, with exercise, diet, medications, medical interventions etc., suspecting one cause after another, while, our departure from the natural light and dark cycle cues, seems to be the single most probable cause for the prevalence of these lifestyle diseases. 

Fig 1.6 - Light and Dark Cycle?

Serious efforts are underway to restore our original balance of light and dark cycle by various research and standards organizations around the world. Growing evidence indicates the urgent need for us to sync ourselves with natural cycles, which can improve our overall physical and mental health, happiness, concentration, alertness, memory and performance. We have only barely begun to understand the impact of light and dark cycle on our health. The American Medical Association (AMA) has adopted a resolution that it supports the need for further research into the health effects of light and the development of new lighting technologies to reduce the effects of artificial light on our circadian rhythms.

We have our choices to either wait for a few more decades for further proof or to look at the existing proof from the past few decades and use a common sense approach to act early and sync ourselves with nature.

Healthy lighting of your homes is all about restoring that balance of light and dark cycle around us. This book is not about medical advice or light therapy or dark therapy, but a book which will empower you to create healthy lighting design for your homes. Metamorphose your home from an ‘one-size-fits-all’ lighting habitat into two distinct habitats, one which glorifies light and the other which glorifies darkness. Depending on your working hours, as a day worker or as a shift worker and your family’s needs, you can judiciously surround yourself and your family with your biological day or biological night at the touch of a switch. Unlike exercise or diet, which requires a conscious effort, healthy lighting of your home will work at a subconscious level to achieve a healthy life style, effortlessly. While great amount of effort, resources and emotional capital is spent on achieving a healthy life style, healthy lighting of your homes could be the most effective, most effortless, most economical and the fastest means to achieve a healthy life style.

What do you think? Share your comments below.

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I aim to spread awareness on the subject of Healthy Lighting designs to facilitate co-creation of healthy lighting at home, work and other social spaces. My posts can be accessed at Archinect  and Linkedin Group. I also have a self published book "Healthy Lighting of your Homes" at Amazon.