The aging eye filters out blue light, affecting circadian rhythm and health in older adults.

THE INVESTIGATORS

Dr. Martin Mainster and Dr. Patricia Turner, University of Kansas School of Medicine.

For decades, scientists have looked for explanations as to why certain conditions occur with age, among them memory loss, slower reaction time, insomnia and even depression. They have scrupulously investigated such suspects as high cholesterol, obesity, heart disease and an inactive lifestyle.

Now a fascinating body of research supports a largely unrecognized culprit: the aging of the eye.

The gradual yellowing of the lens and the narrowing of the pupil that occur with age disturb the body’s circadian rhythm, contributing to a range of health problems, these studies suggest. As the eyes age, less and less sunlight gets through the lens to reach key cells in the retina that regulate the body’s circadian rhythm, its internal clock.

“We believe the effect is huge and that it’s just beginning to be recognized as a problem,” said Dr. Patricia Turner, an ophthalmologist in Leawood, Kan., who with her husband, Dr. Martin Mainster, a professor of ophthalmology at the University of Kansas Medical School, has written extensively about the effects of the aging eye on health.

Circadian rhythms are the cyclical hormonal and physiological processes that rally the body in the morning to tackle the day’s demands and slow it down at night, allowing the body to rest and repair. This internal clock relies on light to function properly, and studies have found that people whose circadian rhythms are out of sync, like shift workers, are at greater risk for a number of ailments, including insomnia, heart disease and cancer.

“Evolution has built this beautiful timekeeping mechanism, but the clock is not absolutely perfect and needs to be nudged every day,” said Dr. David Berson, whose lab at Brown University studies how the eye communicates with the brain.

So-called photoreceptive cells in the retina absorb sunlight and transmit messages to a part of the brain called the suprachiasmatic nucleus (S.C.N.), which governs the internal clock. The S.C.N. adjusts the body to the environment by initiating the release of the hormone melatonin in the evening and cortisol in the morning.

Melatonin is thought to have many health-promoting functions, and studies have shown that people with low melatonin secretion, a marker for a dysfunctional S.C.N., have a higher incidence of many illnesses, including cancer, diabetes and heart disease.

It was not until 2002 that the eye’s role in synchronizing the circadian rhythm became clear. It was always believed that the well-known rods and cones, which provide conscious vision, were the eye’s only photoreceptors. But Dr. Berson’s team discovered that cells in the inner retina, called retinal ganglion cells, also had photoreceptors and that these cells communicated more directly with the brain.

These vital cells, it turns out, are especially responsive to the blue part of the light spectrum. Among other implications, that discovery has raised questions about our exposure to energy-efficient light bulbs and electronic gadgets, which largely emit blue light.

But blue light also is the part of the spectrum filtered by the eye’s aging lens. In a study published in The British Journal of Ophthalmology, Dr. Mainster and Dr. Turner estimated that by age 45, the photoreceptors of the average adult receive just 50 percent of the light needed to fully stimulate the circadian system. By age 55, it dips to 37 percent, and by age 75, to a mere 17 percent.

“Anything that affects the intensity of light or the wavelength can have important consequences for the synchronization of the circadian rhythm, and that can have effects on all types of physiological processes,” Dr. Berson said.

Several studies, most in European countries, have shown that the effects are not just theoretical. One study, published in the journal Experimental Gerontology, compared how quickly exposure to bright light suppresses melatonin in women in their 20s versus in women in their 50s. The amount of blue light that significantly suppressed melatonin in the younger women had absolutely no effect on melatonin in the older women. “What that shows us is that the same amount of light that makes a young person sit up in the morning, feel awake, have better memory retention and be in a better mood has no effect on older people,” Dr. Turner said.

Another study, published in The Journal of Biological Rhythms, found that after exposure to blue light, younger subjects had increased alertness, decreased sleepiness and improved mood, whereas older subjects felt none of these effects.

Researchers in Sweden studied patients who had cataract surgery to remove their clouded lenses and implant clear intraocular lenses. They found that the incidence of insomnia and daytime sleepiness was significantly reduced. Another study found improved reaction time after cataract surgery.

“We believe that it will eventually be shown that cataract surgery results in higher levels of melatonin, and those people will be less likely to have health problems like cancer and heart disease,” Dr. Turner said.

That is why Dr. Mainster and Dr. Turner question a practice common in cataract surgery. About one-third of the intraocular lenses implanted worldwide are blue-blocking lenses, intended to reduce the risk of macular degeneration by limiting exposure to potentially damaging light.

But there is no good evidence showing that people who have cataract surgery are at greater risk of macular degeneration. And evidence of the body’s need for blue light is increasing, some experts say.

“You can always wear sunglasses if you’re in a brilliant environment that’s uncomfortable. You can remove those sunglasses for optimal circadian function, but you can’t take out the filters if they’re permanently implanted in your eyes,” Dr. Mainster said.

Because of these light-filtering changes, Dr. Mainster and Dr. Turner believe that with age, people should make an effort to expose themselves to bright sunlight or bright indoor lighting when they cannot get outdoors. Older adults are at particular risk, because they spend more time indoors.

“In modern society, most of the time we live in a controlled environment under artificial lights, which are 1,000 to 10,000 times dimmer than sunlight and the wrong part of the spectrum,” Dr. Turner said.

In their own offices, Dr. Mainster and Dr. Turner have installed skylights and extra fluorescent lights to help offset the aging of their own eyes.

A beam of white light is made up of all the colours in the spectrum. The range extends from red through to violet, with orange, yellow, green and blue in between. But there is one colour that is notable by its absence.

Pink (or magenta, to use its official name) simply isn’t there. But if pink isn’t in the light spectrum, how come we can see it?
Here’s an experiment you can try: stare at the pink circle below for about one minute, then look over at the blank white space next to the image. What do you see? You should see an afterimage. What colour is it?

You should have seen a green afterimage, but why is this significant?
The afterimage always shows the colour that is complementary to the colour of the image. Complementary colours are those that are exact opposites in the way the eye perceives them.
It is a common misconception that red is complementary to green. However, if you try the same experiment as above with a red image, you will see a turquoise afterimage, since red is actually complementary to turquoise. Similarly, orange is complementary to blue, and yellow to violet.

All the colours in the light spectrum have complements that exist within the spectrum – except green. There seems to be some kind of imbalance. What is going on? Is green somehow being discriminated against?

The light spectrum consists of a range of wavelengths of electromagnetic radiation. Red light has the longest wavelength; violet the shortest. The colours in between have wavelengths between those of red and violet light.

When our eyes see colours, they are actually detecting the different wavelengths of the light hitting the retina. Colours are distinguished by their wavelengths, and the brain processes this information and produces a visual display that we experience as colour.

This means that colours only really exist within the brain – light is indeed travelling from objects to our eyes, and each object may well be transmitting/reflecting a different set of wavelengths of light; but what essentially defines a ‘colour’ as opposed to a ‘wavelength’ is created within the brain.

If the eye receives light of more than one wavelength, the colour generated in the brain is formed from the sum of the input responses on the retina. For example, if red light and green light enter the eye at the same time, the resulting colour produced in the brain is yellow, the colour halfway between red and green in the spectrum.

So what does the brain do when our eyes detect wavelengths from both ends of the light spectrum at once (i.e. red and violet light)? Generally speaking, it has two options for interpreting the input data:

a) Sum the input responses to produce a colour halfway between red and violet in the spectrum (which would in this case produce green – not a very representative colour of a red and violet mix)
b) Invent a new colour halfway between red and violet

Magenta is the evidence that the brain takes option b – it has apparently constructed a colour to bridge the gap between red and violet, because such a colour does not exist in the light spectrum. Magenta has no wavelength attributed to it, unlike all the other spectrum colours.

The light spectrum has a colour missing because it does not feel the need to ‘close the loop’ in the way that our brains do. We need colour to make sense of the world, but equally we need to make sense of colour; even if that means taking opposite ends of the spectrum and bringing them together.

Well, now we’ve got that sorted out, explain this: stare at the dot in the middle of the image below – you should see all the colours melt away.

You can find out more about Liz on her Nullpage.

In this optical illusion you can notice a green circling dot, if you fixate your gaze on the cross. The green dot does not exist in the picture proper but is produced by the retina as an afterimage complimentary in color to the magenta dots

-Biotele

A note from Biotele:

It has come to my attention that some readers are confused by Liz Elliot’s title of this article. Some readers have debated that magenta is a color, especially important in reflective media like paper. And many printers are based on the CMYK color scheme, where M stands for magenta. It is my opinion that the people debating the title have missed the point of the article.

Magenta is an “extraspectral” color. Sir Isaac Newton noticed that magenta did not exist in the spectrum of colors from white light when he played with prisms. But when he superimposed the red end of the spectrum on to the blue end, he saw the color magenta (this can be done with two prisms to make two spectral spreads, “rainbows”):

Magenta is the only color that does not exist as a single wavelength of light. Some readers suggested that browns only exist as a mixture of wavelengths. But browns are dark shades of red and yellows and some browns can be generated by a low intensity single wavelength of red. For example 133:0:0 in the RGB scheme is brown (called maroon).

Brown and green perception are very important in the animal world because they make the contrast between wood, dirt and leaves. So brown is sensed as a different color from red and yellow for evolutionary reasons. In most animals, the eye is also especially sensitive to green for the same reason.

The precise title for Liz Elliot’s article could have been “Magenta is not a spectral color”, “magenta is not in the rainbow” or “Magenta does not have a wavelength”. But the point conveyed by her article is that color perception is not in a one to one correspondence with the physical world. Therefore for those that believe that color represents a wavelength of light then magenta is not a color.

In summary, the representation of colors is solely dependent on the brain and color is only experienced in the mind. Light is colorless and color is a Quale.

Inspired by “Superluniem”, designer Eisuke Tachikawa, made ​​a nice lamp in the form of the moon. The data were taken from the lunar orbiter Kaguya. Hypnotic object?
I think all fans of astronomy would be pleased to have one.

Energy Saving Light Bulb.

Light up the World (LUTW) was the first international development organization dedicated to illuminating the lives of the world’s poor by providing affordable, safe, healthy, efficient, and environmentally responsible lighting.

In 1997, Dr. Dave Irvine-Halliday, a Professor of Electrical Engineering at the University of Calgary, had the vision to use LED lighting to bring practical, economical, and environmentally safe lighting to the developing world. While on sabbatical in Nepal, Dave visited local villages and was struck by the poor conditions of the people. Most of them were relying on kerosene lamps which produced little light and filled the homes with dangerous smoke. As the annual income of the Nepalese villagers averaged $200 USD, Dr. Irvine-Halliday realized that there was a great need for simple, safe, healthy, affordable and rugged lighting.

Dave had been working with LEDs for more than two decades, and spent most of 1997 and 1998 trying to make an acceptable white light from various combinations of colored indicator LEDs. He made white light but it was simply not bright enough to be of any practical use in the developing world. Nichia, a Japanese company, had invented a bright White LED a few years earlier and Dave immediately requested samples. The ‘eureka’ moment occurred when Dave lit his first White Light Emitting Diode.

In 1999, Dr. Irvine-Halliday and his wife, Jenny, tested their prototype WLED lamps in a number of Nepali villages and the response from the villagers was so absolutely positive that they knew what they’d be doing with the rest of their lives.  In 2000, they returned to Kathmandu and with the assistance of their Nepali friend, Muni Raj Upadhyaya, lit the first four villages in the world with WLED lighting, thus laying the pioneering origins for the development of LUTW into a global lighting initiative.

Together with Ken Robertson, Roy Moore and Pauline Cummings, Light Up The World was  established as a legal entity in 2002. From a singular idea born among the poor, LUTW has grown into a global development organization reaching out to even the remotest areas of the world.

Through generous support from interested individuals, corporations, host country organizations, international foundations and industrial partners, LUTW has brought light to more than 26,000 homes in over 50 countries around the world from Afghanistan to Zambia. Close to 1 million people have been impacted directly by this innovative approach to development.

What to Do if a Compact Fluorescent Light (CFL) Bulb or Fluorescent

Tube Light Bulb Breaks in Your Home: Detailed Recommendations

CLICK HERE to view the detailed recommendations.

Fisher Marantz Stone Tribute in Light.mov – YouTube.