Circadian photoreception: ageing and the eye's important role in systemic health.
Olafur Pall Olafsson
reading the full text, it is free through pubmed and is a good
reading. This reminds me that I am going to need to buy some full
spectrum light bulbs later this year to use for the dark winters here
in Iceland.
Br J Ophthalmol. 2008 Nov;92(11):1439-44. Epub 2008 Aug 29.
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Circadian photoreception: ageing and the eye's important role in
systemic health.
Turner PL, Mainster MA.
Department of Ophthalmology, University of Kansas School of
Medicine, Prairie Village, KS 66208-3444, USA. pltur...@att.net
AIM: To analyse how age-related losses in crystalline lens
transmittance and pupillary area affect circadian photoreception and
compare the circadian performance of phakic and pseudophakic
individuals of the same age. METHODS: The spectral sensitivity of
circadian photoreception peaks in the blue part of the spectrum at
approximately 460 nm. Photosensitive retinal ganglion cells send
unconscious information about environmental illumination to non-visual
brain centres including the human body's master biological clock in
the suprachiasmatic nuclei. This information permits human physiology
to be optimised and aligned with geophysical day-night cycles using
neural and hormonal messengers including melatonin. Age-related
transmittance spectra of crystalline lenses and photopic pupil
diameter are used with the spectral sensitivity of melatonin
suppression and the transmittance spectra of intraocular lenses (IOLs)
to analyse how ageing and IOL chromophores affect circadian
photoreception. RESULTS: Ageing increases crystalline lens light
absorption and decreases pupil area resulting in progressive loss of
circadian photoreception. A 10-year-old child has circadian
photoreception 10-fold greater than a 95-year-old phakic adult. A 45-
year-old adult retains only half the circadian photoreception of early
youth. Pseudophakia improves circadian photoreception at all ages,
particularly with UV-only blocking IOLs which transmit blue
wavelengths optimal for non-visual photoreception. CONCLUSIONS: Non-
visual retinal ganglion photoreceptor responses to bright, properly
timed light exposures help assure effective circadian photoentrainment
and optimal diurnal physiological processes. Circadian photoreception
can persist in visually blind individuals if retinal ganglion cell
photoreceptors and their suprachiasmatic connections are intact.
Retinal illumination decreases with ageing due to pupillary miosis and
reduced crystalline lens light transmission especially of short
wavelengths. Inadequate environmental light and/or ganglion
photoreception can cause circadian disruption, increasing the risk of
insomnia, depression, numerous systemic disorders and possibly early
mortality. Artificial lighting is dimmer and less blue-weighted than
natural daylight, contributing to age-related losses in unconscious
circadian photoreception. Optimal intraocular lens design should
consider the spectral requirements of both conscious and unconscious
retinal photoreception.
Publication Types:
* Research Support, Non-U.S. Gov't
* Review
PMID: 18757473 [PubMed - indexed for MEDLINE]
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John Hasenkam
blue light. Even if you get enough sleep, constantly changing circadian
rhythms can cause problems. I read one study which found that even with
regular sleep trans timeline aircrews demonstrated reductions in cognitive
function and some, probably a just a little, temporal lobe atrophy.
There could also be a problem with many computer monitors because these
release large amounts of blue light. This will inhibit melatonin which in
turn can raise dopamine levels. Hence circadian disruption could be
occurring simply by spending all night on the computer, as I do. Fortunately
for me though I'm legally blind in one eye from optic nerve damage, hence
the effect is less pronounced. Another downside is constant exposure to blue
light may damage the eyes, particularly in those with retinal conditions.
John.
--
http://healthycuriousity.blogspot.com/
"Olafur Pall Olafsson" <olafu...@yahoo.com> wrote in message
news:b0fa50f7-50e9-4ea1...@y17g2000yqn.googlegroups.com...
Olafur Pall Olafsson
> Circadians are principally set by amacrine cells in the retina responding to
> blue light. Even if you get enough sleep, constantly changing circadian
> rhythms can cause problems. I read one study which found that even with
> regular sleep trans timeline aircrews demonstrated reductions in cognitive
> function and some, probably a just a little, temporal lobe atrophy.
>
> There could also be a problem with many computer monitors because these
> release large amounts of blue light. This will inhibit melatonin which in
> turn can raise dopamine levels. Hence circadian disruption could be
> occurring simply by spending all night on the computer, as I do. Fortunately
> for me though I'm legally blind in one eye from optic nerve damage, hence
> the effect is less pronounced.
Unfortunately for you being legally blind in one eye will also reduce
the signal to the brain when waking up and during the day when such a
signal is beneficial, for several reasons mentioned in the full text
of the study. Regarding circadian disruption caused by computer
monitors and other sources of artificial light there is a simple and
pretty effective solution to that. Simply get yourself glasses that
block the blue wavelengths that send the signal to the eyes. I myself
got one of these: https://www.lowbluelights.com/detail.asp?id=26 I
start wearing them an hour or two before going to sleep. I also put
them on if I happen to wake up in the middle of the night to urinate,
to cause less of a disruption in sleep when turning on the lights when
going to the bathroom. I recommend these glasses, I have found them to
be quite effective.
> Another downside is constant exposure to blue
> light may damage the eyes, particularly in those with retinal conditions.
That is the irony, the very same blue light that sends the strongest
photoreceptor response to the brain also damages the eyes. The result
is that, as the eyes accrue damage with age, even more blue light is
needed to send a signal of similar strength to the brain.
John Hasenkam
Yes, I've always had problems with sleep regulation. Mind you, not that any
doctor could discern why, another thing I had to figure out for myself ...
.
Some time ago I helped develop a regime for a girl with Stargardts and
advised the use of blue filtered sunglasses. The irony is that many people
with visual impairment rely heavily on computers and so could be
exacberating their condition. I don't know if the Fighting Blindness
Foundation is aware of this but I hope so.
The idea of minimising light exposure when waking at night is very
important. Dement, who started the sleep lab at Stanford, even advises uses
low lighting. I use a sleep mask when sleeping. Sleep mask plus ear plugs
can have a profound effect on sleep. Dement's book, "The Promise of Sleep"
is good for those not familiar with the importance of sleep, it has some
valuable advise. He goes so far as to advise that good sleep is as important
as diet and exercise.
All the best,
John.
"Olafur Pall Olafsson" <olafu...@yahoo.com> wrote in message
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