Does closing your eyes conserve energy?

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In summary: Pupillary reflex does contribute but it is mainly due to the reforming of rhodopsin, taken from wiki;In biological night vision, molecules of rhodopsin in the rods of the eye undergo a change in shape as they absorb light. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to a spectrum of light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark. Rhodopsin in the human rods is less sensitive to the longer red wavelengths of light, so many people use red light to help preserve night vision as it only slowly depletes the
  • #1
cool_walking_
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I'm no scientician, so I was wondering if your eyes not getting any light would actually decrease the amount of energy you'd be using?
 
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  • #2
cool_walking_ said:
I'm no scientician, so I was wondering if your eyes not getting any light would actually decrease the amount of energy you'd be using?

Why exactly do you think that would happen?
 
  • #3
'Cause I don't know how eyes work and thought maybe if they "weren't doing anything" they wouldn't consume as much energy. Obviously they would still be getting some light coming through the eyelids, but less of it, at least.
 
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  • #4
cool_walking_ said:
'Cause I don't know how eyes work and thought maybe if they "weren't doing anything" they wouldn't consume as much energy. Obviously they would still be getting some light coming through the eyelids, but less of it, at least.
What are your concerns about "energy use"?
 
  • #5
Your brain could conceivably use more energy trying to interpret what's going on around you in the absence of sight information than you'd save in the absence of processing the sight information you were shutting out.
 
  • #6
When light enters the eye it breaks down a molecule known as rhodopsin. The breakdown of this chemical activates a signalling pathway in a photoreceptor cell that culminates in a signal being sent to the brain. The photoreceptor continually reforms the rhodopsin so that you can continually see. I'm dredging this memory way up from high school but I'm pretty sure that if you close your eyes your photoreceptors will continue to synthesise rhodopsin for up to 50 minutes without light; this is why when you switch off the light at night it seems pitch black but if you wake up a few hours later everything is a lot clearer. So from that simple point of view when your photoreceptors are not being stimulated with light after 50 minutes they become minutely less metabolically active. Also the nerves that transmit the impulse would be minutely less active.

However the energy this would save would be far less than negligible, a bit like turning off a single lightbulb in a city. And as has been pointed out there are other factors at play like whether or not the brain uses more energy in other areas to compensate for the lack of vision.
 
  • #7
Thanks.

Evo said:
What are your concerns about "energy use"?
Ryan_m_b said:
However the energy this would save would be far less than negligible, a bit like turning off a single lightbulb in a city.
I was really just curious. I don't think I'm going to set up a human-powered energy farm anytime soon :tongue: . I happened to get up in the middle of the night for a midnight snack and thought it might be interesting to do so with my eyes closed. I was sufficiently amused by the experience and got to thinking about the concept of this thread.

And as has been pointed out there are other factors at play like whether or not the brain uses more energy in other areas to compensate for the lack of vision.
This occurred to me as well, but it sounded to me like something that would be too complicated for people to have figured out, yet, so I'd have to settle for this one aspect of the total answer :tongue: .
 
  • #8
beside energy consumed by the brain to interprete images ,and the neglicable energy used for rhodopsin synthesis , there is also energy consumed by the eyes' muscles used to keep both eyes focused at a single point
 
  • #9
Ryan_m_b said:
this is why when you switch off the light at night it seems pitch black but if you wake up a few hours later everything is a lot clearer.

I think this is due to aquiring your "night vision", not because your receptors are doing anything different. Houshold lights are more than enough to keep your pupils from opening to their maximum extent.
 
  • #10
Drakkith said:
I think this is due to aquiring your "night vision", not because your receptors are doing anything different. Houshold lights are more than enough to keep your pupils from opening to their maximum extent.
Pupillary reflex does contribute but it is mainly due to the reforming of rhodopsin, taken from wiki;
Biological Night Vision said:
In biological night vision, molecules of rhodopsin in the rods of the eye undergo a change in shape as they absorb light. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to a spectrum of light, the pigment immediately bleaches, and it takes about 30 minutes to regenerate fully, but most of the adaptation occurs within the first five or ten minutes in the dark. Rhodopsin in the human rods is less sensitive to the longer red wavelengths of light, so many people use red light to help preserve night vision as it only slowly depletes the eye's rhodopsin stores in the rods and instead is viewed by the cones.
 
  • #11
Ryan_m_b said:
Pupillary reflex does contribute but it is mainly due to the reforming of rhodopsin, taken from wiki;

Interesting! Everything I've ever read has just been about the size of the pupil.
 
  • #12
Drakkith said:
Interesting! Everything I've ever read has just been about the size of the pupil.
If you want a cool and simple experiment to do at home blindfold one eye making sure that there is absolutely no light going into that eye for about an hour. After the hour is up you can either go into a room that is pitch black or (if it's easier) do this at night and turn off all the lights. Regardless once you are in a pitch black room and can't see anything take off the blindfold and compare how much you can see out of each eye. It really is amazing!
 
  • #13
ShannonW said:
I'm curious to know how much energy the brain uses compared with the energy to move and breathe and for your heart to pump blood. I wonder what the calorie intake is for those who are in long-term comas? Since they are only using their minds, their heart and their lungs although many are on machines that breathe for them, so how much energy does it take to sit there motionless? I would assume the muscles would still need energy to fight off atrophy.
The brain is massively energy intensive, I have a vague recollection of being told that it consumes 20% of our energy in a lecture a long time ago (but take that with a pinch of salt). As for coma patients it seems they still need 2400 calories a day according to this article on coma patient care. That doesn't really surprise me because even living a sedentary life the body uses a lot of energy.
 
  • #14
Ryan_m_b said:
...if you close your eyes your photoreceptors will continue to synthesise rhodopsin for up to 50 minutes without light; this is why when you switch off the light at night it seems pitch black but if you wake up a few hours later everything is a lot clearer.
No. The reason for the difference is your pupils - they take as much as 30 minutes to fully dilate.
 
  • #15
DaveC426913 said:
No. The reason for the difference is your pupils - they take as much as 30 minutes to fully dilate.

Doesn't post #10 explain why?
 
  • #16
Ryan_m_b said:
Pupillary reflex does contribute but it is mainly due to the reforming of rhodopsin, taken from wiki;

It seems that the full story is even more complex than just manufacturing pigment. There is an adaptive shift in neural processing style as well. Gotta love the sophistication of the brain!

As illumination declines, the visual system starts conserving light in three ways. First, inhibitory responses weaken, and eventually stop. Second, inhibition is replaced by convergence, where the receptor outputs sum together to increase sensitivity but further reduce resolution. Third, there is more available photopigment as light declines.

http://www.visualexpert.com/Resources/nightvision.html
 
  • #17
Drakkith said:
Doesn't post #10 explain why?

Sorry. Somehow I managed to skip over a dozen posts. Retracted.
 
  • #18
Ryan_m_b said:
If you want a cool and simple experiment to do at home blindfold one eye making sure that there is absolutely no light going into that eye for about an hour. After the hour is up you can either go into a room that is pitch black or (if it's easier) do this at night and turn off all the lights. Regardless once you are in a pitch black room and can't see anything take off the blindfold and compare how much you can see out of each eye. It really is amazing!

I've done this. It's crazy. It actually feels like there's something blocking your one eye - like a black pillow covering it.

(However, in-and-of-itself it does not confirm or refute the contention re: the pupil versus rhodopsin explanation.)
 

1. Does closing your eyes really conserve energy?

While it may seem intuitive that closing your eyes would conserve energy, the answer is not as straightforward as it may seem. Closing your eyes does reduce the amount of energy needed for visual processing, but it may not have a significant impact on overall energy conservation.

2. How much energy is saved by closing your eyes?

The amount of energy saved by closing your eyes varies depending on factors such as individual metabolism, duration of eye closure, and level of mental activity. Studies have shown that on average, closing your eyes reduces energy consumption by only about 5-10%.

3. Is closing your eyes beneficial for energy conservation?

While the amount of energy saved by closing your eyes may not be significant, there are potential benefits to taking short breaks from visual processing. Closing your eyes can give your brain a chance to rest and recharge, which can improve overall energy levels and focus.

4. Can closing your eyes replace the need for sleep?

No, closing your eyes is not a substitute for sleep. While it may provide a brief break from visual processing, it does not provide the restorative effects of sleep. In fact, closing your eyes for extended periods of time can actually be detrimental to your health and energy levels.

5. Are there other ways to conserve energy besides closing your eyes?

Yes, there are many other ways to conserve energy such as proper nutrition, regular exercise, and getting enough quality sleep. Additionally, practicing good time management and avoiding mental and physical overexertion can also help conserve energy.

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