Eyeball tracking, pupil tracking, and receptivity to light I’ve heard of and understand, and people see it on movies and TV.
But I’m thinking of the visual change (from our point of view, obviously) of the physical object that reflects and refracts light sitting there in a body. And yes, tends to move a lot when in a certain energized state.
You couldn’t tell by sight the difference between, say, a live guy’s arm and the same spot a moment after his death. I’m wondering about eyes: How soon I’d notice what. We see in someone else’s eyes the “fact that they are seeing” in such a refined and rapid way. Like doctors and EMS in pathological cases, we all do different “diagnoses” constantly in milliseconds in so many ways when we face someone, each diagnostic criterion requiring a different milli-second time slice to check.
I’m fascinating by what those parameters are for the “am I talking to a Zombie” or an “about-to-be-Zombie”–otherwise known as when you can tell someone is bored or falling asleep. I’m sure psychologists have studied this up the wazoo.
The image of “the light fading from his eyes” in death must be very old with humans (good book to write if someone hasn’t yet…). HAL was humanized by having its eyespot/pupil lose definition; Terminator 2’s eyes lost luminosity.*
Our eyes aren’t luminous. What changes when?
*The notion that vision is performed by outward-projecting beams stuck around through the Middle Ages, moving from Arab science and adopted in the West.
ETA: I wonder if any photo artist has substituted dead people’s eyes for original ones and fudged the image to explore this that way. Will check.
I’m sure this is crazy talk, but–the eyes rely on muscles to both maintain position and focus in the eyeball. Perhaps the combination of unfocused/unfocusing cornea and the drift of an eyeball whose position is not actively maintained produce a physical change that is perceptible as “the light fading”? Maybe even there is enough of a physical response to light in the environment that the the subtle loss of that response is perceptible–the eyes drift away from the light source and seem to dim?
This might not be the case, if my speculation is correct, for coma/brain trauma victims, but I think the “light fading” image probably isn’t meant to apply to such cases.
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Wouldn’t those be profoundly brain injuired paitents? PVS is a profound brain injuiry. Severe brain injiured people can still have some level of functioning.
Functioning eyes make a saccadic movement (a sudden jump), often quite a large one, on average from about three to five times every second. Many of them are quite large enough to be clearly visible if you watch for them. This does not only happen in an “energized state” (whatever that means), it happens all the time that your vision is actually functioning and you are not not deliberately and effortfully holding your eyes still (which no-one can do very well, or for very long). There are other types of eye movement too, also sometimes visible (plus yet more that are still more frequent, but too small to be seen without instrumentation). The constantly moving eyes of the living will certainly look very different from the unmoving ones of the dead. We may not usually be conscious of how other people’s eyes (still less our own) are constantly on the move, but that does not mean we do not register that something is different, and wrong, when they stop.
Actually it was “Arab” (actually Egyptian Muslim) science that discovered that the eyes do not emit beams (as some, but not all ancient theorists had believed, along with some earlier Muslims), but, rather, focus them into an image. Medieval westerners learned about this from the Muslims.
Mind you, once you understand how central eye movement is to vision, and how it is so frequent, and under tight direction by the brain, the old “emission” theories of vision cease to sound so crazy. There are no emitted beams, but the eyes are not passive receivers of light, as theorists from Alhacen, to Kepler, to late 20th century cognitive scientists like David Marr regarded them, but (as the emission theorists thought, though for not quite the right reasons) active gatherers of visual information.
Yes, I apologize for writing badly. By al-Hazen was the reception theory promoted, and gradually picked up. You’re also right by noting in how many cases it’s 6-of-1-half a dozen of the other. Da Vinci’s studies in vision and perspective are masterful. Plus thanks for reminding me to look at Marr again.
Well I rather hope you will not look at Marr again, because my point was that he was profoundly wrong about vision. (Actually, his book takes its main wrong turn in its first sentence.) Since then, there has been a revolution in eye movement studies that has turned visual theory upside down. Look at people like Dana Ballard, Mary Hayhoe, Iain Gilchrist, Kevin O’Regan, Alva Noë, Michael Land, Benjamin Tatler, Michael Spivey, Daniel Richardson, Yiannis Aloimonos…
Anyways, I forgot to mention in my earlier posts that another important factor in “dead eyes” is the fact that they are no longer being lubricated by frequent blinking, so the surface will dry out and lose its luster. Lubrication is not just from tear fluid, but oil from tiny glands all along the edge of the eyelid. I doubt that this is as noticeable as the lack of movement, and the effect will take a little while toi appear, but it will certainly change their appearance.
I should also have pointed out that the eye muscles are controlled by cranial nerves that come straight from the brain, bypassing the spinal cord, which is why injuries that lead to quadriplegia, complete bodily paralysis, leave eye movements and their control intact.