Can you look at your own eyeball?

[Atamasama]

Re: Is exposure to small amounts of radiation beneficial?

In the “MEDICAL QUESTIONS WE’RE STILL THINKING ABOUT” section at the end of the article, a Donald Carr asks:

Assume one can take one’s eyeball out of its socket and hold it a couple of inches away while still connected to the brain by the optic nerve. Now, if you turn this eye around so it is looking straight into your other eye, what would you see?

I would think that actually removing your eyeball shouldn’t be necessary. The question is essentially asking what you would see if you could look at one eye with the other eye. To answer that, you would only need to devise a simple device with a few mirrors similar to a periscope, such that the mirrors bounce light around in a U-shape so that you can see each eye with the other eye.

I expect that even going that far isn’t necessary, it’s easy to speculate on what you’d see. Simply, each eye would see the other eye. It would be slightly disorienting but not greatly. To replicate the effect of seeing something completely different out of each eye at the same time, look through one side of a pair of binoculars or a telescope while keeping the other eye open. The two images superimpose each other slightly in the mid-range of your vision but other than that it’s not unlike looking at two pictures side-by-side.

Anyway, I thought I’d offer my opinion on what seems like a very bizarre question, which should have a very simple answer.

[redhead_pt]

This is quite simple, since each eyeball projects a distinct image into the visual cortex.

Look into a mirror which is a couple of inches away from you and close one eye. This is what the detached eye would see. The eyeball which remains in your head would see a disembodied eyeball, and presumably also the hand holding it in place.

And, because of our stereoscopic vision, the brain would attempt to superimpose these two images, giving rise to what would likely be a ghostly (ie. partially translucent) visage, and a blood-soaked palm.

The effect is akin to what happens when you look at a TV while holding a hand two inches in front of one eye. Your hand appears transparent…

[njtt]

@redhead_pt

This is quite simple, since each eyeball projects a distinct image into the visual cortex.

Look into a mirror which is a couple of inches away from you and close one eye. This is what the detached eye would see. The eyeball which remains in your head would see a disembodied eyeball, and presumably also the hand holding it in place.

And, because of our stereoscopic vision, the brain would attempt to superimpose these two images, giving rise to what would likely be a ghostly (ie. partially translucent) visage, and a blood-soaked palm.

NO

First of all, there have been quite a lot of experiments done that present different, inconsistent images to either eye. You do not see ghostly, superimposed images, rather you experience switches at irregular intervals between seeing what is presented to one eye and seeing what is presented to the other.

The eyes do not work like cameras, projecting “images” back to the brain, they work by seeking and extracting visual information from the environment. Furthermore, removing an eyeball from its socket would severely disrupt its proper functioning. The optic nerve, which send the signal back to the brain, is not its only connection. A normally functioning eyeball is controlled by muscles that move it about in its socket, with great frequency and great precision, and in a way that is tightly coordinated with the inflowing information from the optic nerve and the informational needs of the organism. All this coordination would be lost if the eye were removed from its socket. The brain would presumably still be sending out signals to the muscles to move the eye, but it would not be moving in accordance with those signals, but in a quite different way, controlled by the hand holding it. I should expect that the brain would have great difficulty making sense of the signals coming down the optic nerve from the disembodied eye. How that would manifest in visual experience is hard to predict, but my best guess is that, for the most part, the visual information from the disembodied eye would just be ignored by the brain as uninterpretable, and the visual experience coming from the eye still in place would predominate (that is more or less what happens in the experiments mentioned above, except that in those the information presented to each eye makes sense on its own, just not when combined with that presented to the other, so the brain switches between treating one eye and then the other as the “good,” properly functioning, source.)

To the OP, I see no reason why the periscope arrangement you suggest would not work, but, as you would be presenting different images to either eye, presumably, as in the experiments, your experience would switch irregularly between one eye and the other. I should imagine that would be pretty confusing and disorienting. But why go to all that trouble when you can simply use a regular mirror to look at your eyes with no problems at all?

[Atamasama]

@njtt

Furthermore, removing an eyeball from its socket would severely disrupt its proper functioning. The optic nerve, which send the signal back to the brain, is not its only connection. A normally functioning eyeball is controlled by muscles that move it about in its socket, with great frequency and great precision, and in a way that is tightly coordinated with the inflowing information from the optic nerve and the informational needs of the organism. All this coordination would be lost if the eye were removed from its socket. The brain would presumably still be sending out signals to the muscles to move the eye, but it would not be moving in accordance with those signals, but in a quite different way, controlled by the hand holding it. I should expect that the brain would have great difficulty making sense of the signals coming down the optic nerve from the disembodied eye. How that would manifest in visual experience is hard to predict, but my best guess is that, for the most part, the visual information from the disembodied eye would just be ignored by the brain as uninterpretable, and the visual experience coming from the eye still in place would predominate (that is more or less what happens in the experiments mentioned above, except that in those the information presented to each eye makes sense on its own, just not when combined with that presented to the other, so the brain switches between treating one eye and then the other as the “good,” properly functioning, source.)

That reminds me of one thing I had wondered about after I made my initial post here. If the eyeball were detached, and pulled away from the face, and then turned around, it may also be turned sideways or even upside-down in the process. Would that register in your mind? How does the mind determine “up” and “down”, is that only through the equilibrioperception that is a function of the vestibular system of the inner ear, or would twisting the eye actually convey a twisting image to the brain? That was the one ramification of the experiment proposed in the original question that couldn’t easily be reproduced, not without doing exactly as Mr. Carr had originally suggested, some way of detaching the eyeball itself.

[ivn1188]

Other studies show that the brain quickly adapts to alterations of visual input. There have been several experiments with goggles that reverse left/right or up/down. The brain adapts quickly; after a week or so, subjects were just as good at hand-eye coordination, etc as before. When the goggles were removed, it took about a week to adapt back.

There are different sets of studies that examine perceptual changes in subjects that have had serious injuries, etc. Those are more difficult to control properly, but even extremely severe visual distortions appear to be perceived as normal vision, much like we are not aware of our blind spot or how movies and tv work

And to address njtt, I think there are some studies out there that involved anesthetizing the ocular musculature, but I don’t recall what the results were.

[njtt]

@ivn1188

And to address njtt, I think there are some studies out there that involved anesthetizing the ocular musculature, but I don’t recall what the results were.

Well, I have read quite a bit of the scientific literature on eye movements and I have never come across any mention of such experiments, which makes me think that if they did occur, the results were not very interesting. (Although if you can recall where you heard of it, I would be very interested to know.) I do know, however, of a case of a young woman whose eye muscles are paralyzed by disease. In order to be able to see (relatively) normally, she has had to learn to make constant small jerky movements of her head, mimicking, as best she can, the movements of healthy eyes. Conceivably, someone with an eyeball held in their hand could eventually learn to do something similar, but I think it would be a lot more problematic.

What you say about adaptation to prism goggles and the like, and to certain sorts of injury to the eyes, is true, but removing one from its socket altogether and expecting it still to function is going way beyond that. (For practical purposes it would not matter much if the removed eye did not function, because the other eye would still be good and one eye is enough to give you pretty good visual function. Really it leaves you with just a slightly diminished field of peripheral vision, and you lose binocular depth. For most purposes, binocular depth is not that important, and motion parallax and other cues provide quite adequate depth information.)

[njtt]

@Atamasama

or would twisting the eye actually convey a twisting image to the brain?

No, as I said, the eye does not convey any image, twisting or otherwise, to the brain. To imagine that it does is to fundamentally misunderstand visual perception. The eye sends information to the brain, or, better still, the brain uses the eye to get information about the environment from the light that is reflected off (or emitted from) things.

[Powers]

@njtt

The eye sends information to the brain, or, better still, the brain uses the eye to get information about the environment from the light that is reflected off (or emitted from) things.

What information is that, if not visual information?
Powers &8^]

[njtt]

Of course it is visual information, since it acquired by the sense of vision. That is what “visual” means.

[nilum]

Assume one can take one’s eyeball out of its socket and hold it a couple of inches away while still connected to the brain by the optic nerve. Now, if you turn this eye around so it is looking straight into your other eye, what would you see?

Your other eye.

It can’t be any type of visual feedback (which I assume is what we’re unsure of here).

Visual feedback happens when the input is also the output.

An example would be a video camera connected directly to a monitor and being pointed at the monitor. The display output is then fed back into the camera input and thus creates a visual feedback loop. It’s also important that light is emitted from the output, put back into the camera, and back out the monitor as light, etc.

For two eyes, you merely have two inputs. The output doesn’t even emit or reflect anything because it’s your brain’s visual cortex.

The other eye would only see the other eye. There is no feedback or distortion that could happen (at least none that I could think of).

What happens when two cameras record each other? Nothing. You get unremarkable recordings of another camera.

What happens when you stare directly into someone else’s eyes? They call you a ‘weirdo’ and move on.

[nilum]

BTW. This is in response to:

Is exposure to small amounts of radiation beneficial?

Tried to edit it in, but… oh well.

[Clothahump]

Assume one can take one’s eyeball out of its socket and hold it a couple of inches away while still connected to the brain by the optic nerve. Now, if you turn this eye around so it is looking straight into your other eye, what would you see?

Don’t know for sure. But you would certainly have a whole new outlook on life.

[Superfluous_Parentheses]

Surely you’d see BOTH eyes, since we’re assuming both eyes are still working correctly, only watching in the opposite direction.

My guess would be that the brain would try to interpret this as if it’s only seeing one eye, more or less the same thing that happens when you press your nose to a mirror - try it!

[rowrrbazzle]

@Clothahump

Don’t know for sure. But you would certainly have a whole new outlook on life.

The phrase “I’ll keep an eye out for you” would have new meaning, too.

[markci]

@njtt

No, as I said, the eye does not convey any image, twisting or otherwise, to the brain. To imagine that it does is to fundamentally misunderstand visual perception. The eye sends information to the brain, or, better still, the brain uses the eye to get information about the environment from the light that is reflected off (or emitted from) things.

A distinction without a difference. An image is information. And you’re talking out of your ass.

[njtt]

@nilum

Your other eye.

It can’t be any type of visual feedback (which I assume is what we’re unsure of here).

Who has suggested or implied that visual feedback would be an issue?

@nilum

An example would be a video camera connected directly to a monitor and being pointed at the monitor. The display output is then fed back into the camera input and thus creates a visual feedback loop. It’s also important that light is emitted from the output, put back into the camera, and back out the monitor as light, etc.

This is beside the point. The eye does not function like, or have the same function as, a video camera.

@Superfluous_Parentheses

Surely you’d see BOTH eyes, since we’re assuming both eyes are still working correctly, only watching in the opposite direction.

As I have explained in some detail, both eyes would not be working correctly.

@markci

A distinction without a difference. An image is information. And you’re talking out of your ass.

An image may be information (more accurately, it contains or conveys information), but not all information is, or is contained in, images. The eye sends information to the brain, it does not send an image to the brain. It is a real and important distinction. If you cannot grasp it, that is not my fault.

I base my assertion on having closely studied the scientific literature on visual perception over a period of about 30 years. I have published on the subject in prestigious, peer reviewed scientific journals. My ass probably knows a whole lot more about the subject than than the whole of you, including what passes for your brain, does.

You fail in terms of logic, knowledge, understanding, and courtesy!

[Powers]

@njtt

Of course it is visual information, since it acquired by the sense of vision. That is what “visual” means.

That, to me, is the very definition of “an image”, though.
Powers &8^]

[John_W.Kennedy]

And the eye, proper, does function like a camera, as anyone knows who’s graduated from Junior High; if we ever chance to forget that, the Fundies will always be there to remind us. It’s the eye-brain system where the analogy breaks down.

[njtt]

@Powers

That, to me, is the very definition of “an image”, though.

To give an example, a detailed description of the appearance of something would be visual information, but it would not be an image.

[njtt]

@John_W.Kennedy

And the eye, proper, does function like a camera, as anyone knows who’s graduated from Junior High; if we ever chance to forget that, the Fundies will always be there to remind us. It’s the eye-brain system where the analogy breaks down.

Well, what you learn in junior high, even if not strictly speaking untrue, does not always provide the best basis for understanding how things really work.

Yes, the optics of the eye are fairly similar to those of a camera, but the analogy starts to become seriously misleading well before you get to the brain. For one thing, if the camera film, or the CCD array that registers the image in a digital camera, were designed anything like the human retina, your photos would show sharp detail and full color only in a very small region (about 2 degrees of visual angle) in the center of the picture, becoming more and more blurry, and with the colors fairly rapidly fading towards gray, towards the edges. There would also be a filigree of lines across your photo, shadows of the blood vessels in the retina that actually come between the light sensitive receptor cell (that are, for some reason, at the back of the retina) and the incoming light.

Also, the retina contains quite a complex neural network that (certainly in some mammalian species, and probably in humans too) can, for instance, distinguish between moving objects and optical movements produced by your own head and eye movements, and can directly detect when something is coming rapidly towards you (“optical looming,” when the apparent angular size of something in the visual field rapidly increases). Thus, probably, one of the signals that goes down the optic nerve could best be interpreted to mean something like “there is something (I can’t say what yet) coming straight at my face - better get out of the way fast!” (There is another example for you of visual information that is not an image, or any component of an image.) Very likely, other, similar sorts of visual processing occur in the retina that we do not know about yet. The ones I have mentioned are both quite recent discoveries.

In addition to all that, if a camera, still or video, constantly jerked, swung and wobbled about the way your eyes do, usually several times every second, you would not get good pictures, and any videos produced would be quite unwatchable. By contrast, if your eyes did not move around like that, you would not be able to see properly.

All in all, the analogy between the eye and a camera is extremely limited, and, though not exactly wrong, is probably more misleading than helpful for those who want to understand vision.