Wow, I didn't know that eye transplants were so close to being a thing! That's amazing for blind people.
While it is still unknown whether he will regain sight, since the May 2023 procedure, the transplanted left eye has shown remarkable signs of health, including direct blood flow to the retina—the area at the back of the eye that receives light and sends images to the brain. Although many questions remain in a case with no precedence, this groundbreaking achievement opens new possibilities for future advancements in vision therapies and related medical fields.
That's kind of the the feeling that I got from chatting up my opthomologist. She cited the sheer complexity and number of nerve fibers (>1 million) going from an eye to the brain is incredible.
Oddly I was always under the impression that eyes were the most commonly harvested organ from organ donors.
Apparently I was wrong and it wasn’t the entire eye but the cornea.
Cornea transplants can successfully restore eyesight in certain patients and it is common because the cornea doesn’t present the same tissue rejections as organs.
Just posting this in case I wasn’t alone in my misunderstanding.
Yep, I have two transplanted corneas, from ~25 and ~30 years ago. No anti-rejection medication needed after (IIRC) 12 months, unlike every other organ, where you need it forever. The cornea (the clear window right at the front of your eye) isn't connected to a blood supply, and gets its oxygen from tears. https://en.wikipedia.org/wiki/Corneal_transplantation
I have a transplanted cornea too (along with an implanted contact lens in the same eye), took me from being unable to resolve detail at any distance to being pretty much 20/20
(Couldn't find a reference in your link, this discusses it in the first few sentences)
((Also, why does mobile wikipedia not have any way to get the contents tab, for linking? I get hiding it by default.. but why not have it available?!))
Indeed, because we haven’t yet figured out how to successfully reintegrate the nerves. So even if the actual eye is transplanted, there will not be vision.
IIRC peripheral neurons can heal, as in, if you cut off a finger and you sew it back on, you can regain feeling in the finger. But CNS neurons have very limited healing ability, which is why spinal cord injuries are so difficult to treat. The optic nerve is considered part of the CNS.
I had crazy optical nerve issues from advanced neurological Lyme earlier this year.
It was like an old VGA cable wasn’t plugged in correctly and the colors didn’t quite line up. Also had a white area appearing in the center of both eyes.
It was scary as heck. I was told not to expect full recovery due to what you stated. I am happy to report that taking my meds + time and I am back to 100%, as far as the vision at least.
First of all, congrats on your recovery! The worst condition I've ever experienced myself was a massive scintillating scotoma, so I kinda can imagine how you felt.
Still, as a neuroscience researcher I am very interested, if possible, in hearing a little bit more details. You mentioned a color shift. Since you compared that with a broken VGA, I assume the colors were attached to actual objects but were incorrect, right? As if someone had played with color filters in Photoshop.
Did you experience color that was "detached" from an object, like a poorly calibrated printing press that shifts one of the colors a bit?
What about the fills? Was it like a random color noise texture or a solid fill but with incorrect color?
It doesn't need to be perfect or even "good", anything would be useful.
Even if he had a dozen or so random nerves form connections and supply signals to be brain, that'd still be massively useful compared to nothing, and the brain should be able to figure out how to use that to reconstruct limited depth perception that wouldn't be possible with just one eye.
I've heard of crazy experiments done in the past, e.g. one where a blind subject was given effectively a braille device on their tongue fed from a camera, so effectively a very low resolution (it might have been 8x8), and the brain was able to start correlating the pressure signals from the tongue with "sight" and the recipient learned how to avoid obstacles using their new tongue sensor.
> The entire left eye and optic nerve were transplanted, and stem cells from the donor’s bone marrow were transplanted along with them in the hopes of helping the optic nerve regenerate.
If the axons in the optic nerve bundle somewhat randomly connect, is the brain able to adjust to that and re-learn how to see? Seems it may have been done in animals successfully?
I would assume that is what happens with babies. Unless human development is that deterministic down to the cellular location level, I would imagine that rod/cone neurons are wired somewhat randomly and the brain spends months sorting out that neuron pathway #16384948 corresponds to the cone(x: 1340, y: 960, .leftEye) while pathway #16380021 corresponds to rod(x: 1280, y:720, .rightEye). But I have no clue so maybe I am completely wrong.
> the brain spends months sorting out that neuron pathway
Yup: but unfortunately, this is one of those things that seems to have a "critical period". (We know this because of experiments on poor defenceless kittens. Thanks, science! (But, I mean, it's decades later and it's got actual medical applications now, and we don't have to re-run the experiments because the results were all written down, so… maybe we should actually thank science for this one.))
IIRC studies have observed ketamine doing this for at least the critical period of language-learning. I would guess that any AMPA antagonist (to tilt things in favor of bottom-up processing) would do the same.
The information travelling down the optic nerve is already processed heavily by the retina. At a minimum, you have compression by differentiation, i.e. a bunch of rods and cones are bundled together by comparing their signal.
But I suppose your point is still possibly valid - just even more complex.
This is a deep philosophical question that gets to the heart of what it is to experience - when it comes to the brains perceptions around colour however we can be relatively confident that the wetwear processing results in the same result, assuming the same input capabilities. (Side note - I spent a lot of time arguing this with my medical school ophthalmologists and neurologists, which is why I have confidence in this particular result)
This is because it isn’t a single photoreceptor picking up, say, 320nm light. Instead you have a range of essentially analog responses across the red, green and blue spectrums, that the brain reconstructs into true colour as we perceive it.
Those with different receiving capabilities (on the one extreme: tetrachromia - those with 4 different colour sensors, who are exclusively women, because they’re on the C chromosome - and on the other end, those with cataracts - witness monet’s later life paintings) help to demonstrate the consistency with which the brain is able to achieve a similar qualia from the underlying stochastic impulses
You're looking at it backwards. The actual question is, how do you know what "red" and "blue" are to begin with? And the answer is, you learn what the colors of things you see are called. You learn that stop signs are red and the sky is blue. And that's how you calibrate your own experiences of color. Whatever you experience when you see a stop sign, that's what you call "red", and whatever you experience when you see the sky, that's what you call "blue".
Color theory is about the ratios between frequencies of light. That's what our brains respond to, along with cultural connotations.
Because color theory works on pretty much everyone, we can be sure that we all perceive the relative difference in colors the same way. But what green is is a figment of your consciousness. What you think color, sight, and all your other senses mean exists only in your mind. Not as a physical process in the brain, but purely as a part of whatever metaphysical process that results in consciousness.
A color is not a real, tangible thing. It's just the way your brain perceives light of a certain frequency. There is no way to describe what that experience is because there's no universal reference. You can't describe color to a blind man, after all.
Unless you believe in some kind of transcendental mind/soul, experiences such as color can't be anything other than physical processes in the brain (and/or the rest of the body).
The fact that we can't identify them with our current level of understanding of the workings of the brain is not very surprising - it is an extremely complex organ and our tools for understanding organs are very primitive in the grand scheme of things.
Not transcendental, no. But consciousness isn't just the physical and chemical reactions in your brain. It's more than the sum of its parts.
The mind is a level of abstraction up from the brain. The mind is what the brain does, not necessarily what it is. Consciousness of course relies on discrete physical reactions in the brain, but in the way that software relies on the discrete transistors in a CPU. Consciousness is the emergent behavior of the system. It exists more on an informational level than physical, even if it is a physical process.
If you call the sky blue and I call the sky blue, that doesn’t mean your interpretation of what is blue matches my interpretation of blue, it just means that we have both agreed linguistically that whatever colour we each see the sky as is blue.
Colour is a construct of the mind based on how we perceive light frequencies, not a tangible thing we can touch.
There's been experiments with upside-down goggles, where people have been able to adapt in a week or two. They claim that after long enough they see the world normally because their vision has actually changed.
I'm not biologist and have no idea if its directly relevant to this procedure, but perhaps this work by Michael Levin's lab could make this hope more optimistic:
Considering the fact that people have regained limited “vision” with implants/bionic eyes, the answer is most likely yes. Though the electronics usually have very limited resolution, I believe second sight’s last one had 40 pixels.
Absolutely amazing feat of medicine, even more astounding is the team of 140 working on the patient over a period of 21 hours.
Recovery is a scary and awesome thing. When I broke my leg and had surgery I was told it was a 50/50 chance of getting nerve damage and loss of sensation to my foot. After many months of "pins and needles" and random pains, I was blessed to have full sensation restored.
I used to imagine in my head the neurons in my leg and ankle talking with each other and saying, "Hey buddy you're supposed to synapse with me, not that other guy over there".
Pretty fascinating stuff, with clear benefits to both sides.
It's always good when they can get an opportunity to try an approach in a "realistic" scenario to see how it turns out, rather than in a lab.
Some does come across as a bit of "let's see what happens" with the eye transplant. I don't see how what comes down to "taking this end and hooking it up to that end" could be expected to work. It's not like plugging an extension cord in, clearly. Some very small-scale structures have to line up exactly right, if its even something that can be done. But I am not in this field, so maybe it is.
It's amazing to me that people do this sort of thing as part of their career ... literally taking off a person's face, "underlying skull", and all the other stuff. Left to continue work on a sight that many wouldn't be able to even glance at during the procedure. It's surreal. Not a job for me, but it's good that there are others out there that are able to do it.
I understand why people are reluctant. If you donate your organs, you don't get a 'death'—as in your loved ones don't get to sit and hold your hands while you die—as you need to be kept 'alive' while the organs are removed. You die on the operating theatre table.
Another issue (the one that worries me) is that anaesthesia isn't always given, but neuromuscular block is, to stop the spinal reflex movements.
>Spinal reflex movements are common and full neuromuscular block is required. Hypertension and increased plasma catecholamine concentrations have been observed during surgery and attributed to spinal reflexes. These can occur spontaneously or on surgical stimulus and have prompted some to suggest that anaesthesia for organ donors is required.
I can't edit my post. You are right. I see bills pending to make it opt-out rather than opt-in, but I was totally mistaken. After researching this for a while after seeing your reply I can not find any states currently doing opt-out.
No. Basically the further the nerve is away from the spine, the better it's able to heal. Central nerves in the spine and brain have almost no ability to heal, but those in the face and hands can usually heal if they're cut.
Even if you physically put spinal nerves back together, they just don't reconnect. We can put them back together, but that's not enough.
Not spinal nerves AFAIK but I just learned a few weeks ago that hand/arm transplants are a thing! In those cases the nerve connections (usually) allow recipients to feel and move the donor limb.