Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: thedoc on 05/11/2016 00:53:02
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Tim and Mark Gladwin asked the Naked Scientists:
Hi. We just tried to leave a question on your answerphone but could not get through, so its back to email.
My son Mark (11) has a really interesting question.
What happens to your pupils when you close your eyes? Do they dilate as they would in the dark?
Looking forward to your answer
Kind Regards Tim & Mark
What do you think?
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If you blink, they don't change size at all.
But I guess you are asking about longer periods...
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...What happens to your pupils when you close your eyes? Do they dilate as they would in the dark? ...
Initiating eye-movements tells the brain to ignore the information from the eyes, as during eye-movement the image on the retina would just be a confusing blur ... https://wikipedia.org/wiki/Saccadic_masking
Something like ...
"Eyes are about to move, ignore visual input, (and buffer (https://en.wikipedia.org/wiki/Chronostasis)), until eyes are stationary".
Possibly something similar occurring during eyelid-movement which overrides automatic pupil dilation.
Something like ...
"Eyelids are about to blink, so it's going to get dark for a moment, but don't increase the aperture".
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Just following up RD's post, I wonder whether any tests have been made of pupil-dilation during sleep.
It would be interesting to discover whether during REM sleep, when we dream of "seeing" all kinds of things, our pupils dilate and contract in response to these "visions".
The practical difficulties of such tests seem great - has anyone attempted them?
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zx16 asked the difficult question about what happens while you are asleep.
I am going to hazard a guess about intermediate durations, where you close your eyes for a period of time, but you remain awake.
- I suspect (without any evidence) that your pupils will open to the extent that they would in a room of similar brightness to your closed eyelids.
This should be easy to test - stand next to a mirror, close your eyes for a minute, then open them, and see if your pupils contract.
2 minutes later: It's not as easy as I thought; by the time my eyes have focused, any pupil shrinking had stabilized....
- I might need to recruit an assistant who tells me when to open my eyelids.
My assistant didn't even need to do the experiment on me - she has done it many times with schoolkids.
- After 60 seconds of eyes closed, there is a visible shrinkin of the pupils when they open their eyes
- But you have to pick the kid with blue eyes; you can't see the change in size with a black pupil and dark-brown iris (like mine).