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I can change the focal point of my eyes on command to a far away point or a close one, and I have noticed that this reliably makes my pupil get slightly larger

I can change the focal point of my eyes on command to a far away point or a close one, and I have noticed that this reliably makes my pupil get slightly larger or smaller.

SamBam 5y ago
Yeah, the article mentions that as the early way the man learned to do it, before being able to directly control the muscle.
monitron 5y ago
That's neat. I wonder if the pupil is actually changing size, or if it's the changing shape of the lens that is making it appear so. If you look into a camera lens as the focus is changed, the inner parts of the camera do appear to change size.
- drewzero1 5y ago
  The eye's lens is behind the iris (unlike a camera which is typically the other way around), so the optics shouldn't affect the apparent pupil size.
  - monitron 5y ago
    Whoa. I had no idea. Thanks for informing me! That's so weird. I had always assumed that the curved front surface of the eye was the lens.
    - uj8efdkjfdshf 5y ago
      You're not wrong - the cornea (front of the eye) has about 3x the refractive power of the lens. Both function as converging lenses, and the only difference is that the refractive power of the lens can be changed.
      - SomeHacker44 5y ago
        ...until age 45 to 50ish, when the lens hardens into a focus close to infinity and you start to need reading glasses. (presbyopia)
- uj8efdkjfdshf 5y ago
  It's the accommodation reflex [0] at work here - pupillary constriction goes hand in hand with a shortening of the focal length of the lens, and the eyes also converge together. This is a brainstem level response, so I doubt there'd be any easy way to dissociate these movements consciously. [0] https://en.wikipedia.org/wiki/Accommodation_reflex https://en.wikipedia.org/wiki/Accommodation_reflex
  - msdrigg 5y ago
    Interesting, this makes sense. Thanks for figuring it out
spoonjim 5y ago
This guy can “tremble” his pupil. It’s not the same at all.
- sethammons 5y ago
  I knew a dozen kids in middle school who would do that. I got to the point I can do it sometimes.
dbtc 5y ago
I recently discovered / figured this out as well, while practicing meditation. I have found it's a great way to relax my eyes periodically while staring at a screen. Still can't move my eyebrows independently though.

I can change the focal point of my eyes on command to a far away point or a close one, and I have noticed that this reliably makes my pupil get slightly larger or smaller.

SamBam 5y ago

Yeah, the article mentions that as the early way the man learned to do it, before being able to directly control the muscle.

monitron 5y ago

That's neat. I wonder if the pupil is actually changing size, or if it's the changing shape of the lens that is making it appear so. If you look into a camera lens as the focus is changed, the inner parts of the camera do appear to change size.

drewzero1 5y ago
The eye's lens is behind the iris (unlike a camera which is typically the other way around), so the optics shouldn't affect the apparent pupil size.
- monitron 5y ago
  Whoa. I had no idea. Thanks for informing me! That's so weird. I had always assumed that the curved front surface of the eye was the lens.
  - uj8efdkjfdshf 5y ago
    You're not wrong - the cornea (front of the eye) has about 3x the refractive power of the lens. Both function as converging lenses, and the only difference is that the refractive power of the lens can be changed.
    - SomeHacker44 5y ago
      ...until age 45 to 50ish, when the lens hardens into a focus close to infinity and you start to need reading glasses. (presbyopia)
uj8efdkjfdshf 5y ago
It's the accommodation reflex [0] at work here - pupillary constriction goes hand in hand with a shortening of the focal length of the lens, and the eyes also converge together. This is a brainstem level response, so I doubt there'd be any easy way to dissociate these movements consciously. [0] https://en.wikipedia.org/wiki/Accommodation_reflex https://en.wikipedia.org/wiki/Accommodation_reflex
- msdrigg 5y ago
  Interesting, this makes sense. Thanks for figuring it out

spoonjim 5y ago

This guy can “tremble” his pupil. It’s not the same at all.

sethammons 5y ago
I knew a dozen kids in middle school who would do that. I got to the point I can do it sometimes.

dbtc 5y ago

I recently discovered / figured this out as well, while practicing meditation. I have found it's a great way to relax my eyes periodically while staring at a screen. Still can't move my eyebrows independently though.