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Article tiré du magazine "Point de vue"
THERE IS A TERRIBLE DEFINITION OF OLD AGE, given to us at the very end of the 16th century by Shakespeare in his own way in As You Like It, “Last scene of all… is second childishnessand mere oblivion, sans teeth, sans eyes, sans taste, sans everything.” and this was at a time when great age could be seen as a blessing!
This is truly an atrocious image that he introduces into the script of a comedy, an image where eyes play their part. The literary genius has nonetheless, and paradoxically, extended to the majority of men and women the unavoidable fate of Man, this fatal stage in their ageing process. Up until recent times, in fact, most people living never even reached the age of presbyopia.
Life expectancy at birth, and life expectancy at the age of 65 have, we can happily say, considerably increased. Infant mortality, horrifying in the past, and seen as an inevitability, decreased in remarkable proportions over the past century, and for the past thirty years the improvements in hygiene conditions and medical progress have led to an impressive reduction in morbidity amongst elderly people, many of whom now live without any major incapacity to over 80 years and beyond. Of course ageing is still inevitable but it has become partially influenceable, even though the biological evolutions that govern it still retain numerous unknowns. Why do we age? The important question that we all ask ourselves still remains, when our past abilities are substituted by new and increasing inabilities that mark every stage on our final journey.
Article from the magazine "Point de vue"
Low-energy light bulbs, TV and computer screens, game consoles and smartphones play havoc with your biological clock.
To most people the purpose of their eyes is vision. However fewer are aware of the eye’s non-visual functions, especially that of controlling the production of melatonin — the sleep hormone.
It was long thought that the eyes of humans and other mammals had only two types of photoreceptors: cones and rods. However research over the last decade has revealed a third type of photoreceptor, quite distinct from rods and cones.
This type of photoreceptor uses a different photopigment called melanopsin, which is less sensitive to light.
Known as “intrinsically photosensitive retinal ganglion cells” (or ipRGCs), these cells, numbering about 3,000, are a subset of ganglion cells. What is surprising is that the only function of these photoreceptors is to communicate directly with the brain. They have no visual function.
These photosensitive cells thus regulate functions other than sight, in particular:
Shortwave blue light stimulating the ipRGC cells in the retina express the pigment melanopsin, which acts through the retinohypothalamic tract to suppress the secretion of melatonin (the sleep hormone) by the pineal gland. This interferes with the ability to fall and stay asleep.
The behavior of humans and other terrestrial animals follow diurnal cycles of light and dark. These cyclical changes in behavior are called circadian rhythms. Circadian rhythms .
Circadian rhythms are biochemical, physiological and behavioral cycles over a period of around 24 hours, governed by a biological clock which is regulated by the frequency of day and night, as perceived by the specialized photoreceptors in the retina.
Despite its low light of 18 lux, a low-energy bulb provokes twice the biological reaction than the far brighter (450 lux) light from an incandescent bulb.
Melatonin also lowers your body temperature during the night, which means you are less alert. It also has an effect on attentiveness, learning and remembering.
Conversely, experiments in France and Sweden on the effects of blue light from car dashboards while driving at night indicate that it’s as good as coffee for keeping the driver alert. Which is why it also interferes with sleep.
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Blue light is everywhere, originally mainly in sunlight. This is nothing new. What has changed is our way of life. In short, we have gone from darkness to light within a few decades. Consider the changes to our habitat, where living spaces are now facing south and have large windows, whereas our elders tended to protect themselves from the sun; then there is extensive exposure of our bodies to sunlight in Western countries where garments are lighter and leisure is geared toward the sun (sea, mountains, ski, etc.). But that’s not all. Two major technologies have emerged in recent years that have contributed to blue light over-exposure: LED lamps and the last generations of screens. At the same time, the elderly are now suffering from age-related macular degeneration (AMD) on a large scale, and the use of screens by all of us, especially the younger generations, is literally exploding. These changes are now giving rise to fears of potentially associated health dangers, and an increasing number of questions.
The blue light wavelengths emitted by TV, computer or smartphone screens, as well as by the new generation of low-energy light bulbs, suppress your production of melatonin, the hormone that regulates your sleep patterns.
Blue light is 100 times more active on the light-sensitive receptors in your retina than the white light from traditional light sources, for the same intensity of light.
The high-tech GoodNight® glasses filter and block this high-energy shortwave light. This protection allows your body to resume production of melatonin. And you’ll find that you quickly resume natural sleep as well.
A round table discussion held in January 2016 – chaired by Professor John Marshall with a panel of experts representing research, ophthalmology, academia and retail optometry – set out to determine the extent to which blue light is a hazard to the human eye and to establish whether it is implicated in disease such as age-related macular degeneration (AMD).
Discussions included the availability of existing research and the likelihood of future studies being conducted, which will help support the increasing body of evidence that blue light is a concern for eye health. They concluded by suggesting how this potential risk should be discussed in the practice environment.
Light is suspected of being a risk factor for major vision-threatening diseases. Yet an equal light exposure can unequally affect people. Multiple intricate factors are responsible for a distinct personal risk profile. The scientific quest in understanding both eye phototoxicity and individual risk profiles can set a turning point towards personalized prevention in the future.
AMD is the leading cause of legal blindness in industrialized countries. It has two forms, atrophic and exudative, and a multifactorial pathogenesis. To cope with the ever-increasing incidence of AMD, retinal specialists resort to three strategies: primary prevention, patient management in clinical practice and prospective medical research aimed at finding new therapies.
In this new digital era, there are new risks for user eyes and new challenges for vision care professionals. Ten experts, optometrists, ophthalmologists and researchers have addressed this broad topic and offer us their experience and thoughts in the form of verbatim comments. This overview has been divided into three main thematic areas: risks and prevention, professional practices, and projections and expectations.