In Sci-Fi the concept of eye-transplants is common enough - what would it take to actually be able to do it?

Submitted by Daniel_Jacksson t3_zvv577 in askscience

In films such as Minority report, Tom Cruise has to get an illegal eye-transplant, by IIRC Peter Stormare, implying that even an black-market "doctor" could get the equipment and have the knowledge to go through with the procedure.

Would the patient require to solely transplant the eyeball or would any nerves, like the optic nerve have to be transplanted too?

A follow-up question; In the TV series Babylon 5, a doctor is able to implant an artificial eye into a patient. The patient would see via a camera that transmitted to the optic nerve (IIRC). I don't recall if the eye-ball was artificially grown or not.

Funny enough the eyeball transmitter has some range so the eye could be ehm.. forgotten somewhere..for a while.

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athomasflynn t1_j1t1fgy wrote

We would need the ability to graft and/or regrow nerve tissue. Something has to carry the visual signals generated by the eye to the brain or its just a useless eye sitting in your head.

For an artificial eye (basically just a camera) we would need the ability to connect and interface electronic components with nerve tissue and the receiver would need to be able to produce a signal that the brain can understand.

We will probably have eye transplants well before bionic eyes. When we do, what you're describing is basically something like a Bluetooth receiver connected directly to the optic nerve where the "eye" is a standalone, battery powered camera that just happens to sit in the eye socket most of the time. Useful, but it would probably be really disorienting when you take it out. I imagine most people would get motion sickness.

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mjbat7 t1_j1thvo8 wrote

Bionic eyes are currently in development by the bionic ear team and they aren't that far away, although it'll probs start with simple shapes with poor resolution. But it's a simpler problem because you can interrogate the patient's optic nerve and augment stimuli to inform the way your device communicates.

On the other hand, transplants are much more challenging - the visual pathway from cone/rod passes through complex, multi-synapse neuronal processing. Neurons tend to degrade quickly and they aren't very good at repair. Then there's the rejection question. So you don't have a good way to figure out if you're connecting the right donor/patient neurons, and even if you did, they'd rapidly degrade.

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athomasflynn t1_j1ur002 wrote

I understand what you're saying but I was talking about something close to or better than human vision. I'd argue that bionic eyes are further along because they're sending a simplified signal. As they ramp up they're going to run into the mapping issues. There's a ton of different procedures and repairs to incentivize improvements in neuron grafting, organ rejection and neurogenesis where the bionic eye challenges seems like it will pull in less R&D money. I might be wrong though, brain implants are getting popular in the startup funding cycle so that might drive crossover breakthroughs.

I'm personally rooting for bionic eyes. I'd like to be able to see like a mantis shrimp in my 70s.

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nubsauce87 t1_j1tramt wrote

Bionic eyes already exist. There was a story this year about how a handful of people who had them went blind because the company that designed them went out of business and stopped supporting them.

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neroute2 t1_j2a1u0e wrote

Were those the extremely limited ones (like a 3x3 grid of pixels)?

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mckulty t1_j1ucr3r wrote

The optic nerve doesn't carry individual pixel information. There are 100 million rods and cones, and only 1 million axons traveling up the optic nerve.

These axons make up the optic nerve behind the eye. The problems with cutting this nerve and connecting another look insurmountable.

  1. the optic nerve axons are long extensions of ganglion cells, but the cell bodies are in the retina. You can't cut these axons and expect them to grow back because the part you cut off will die and the ganglion cells could not figure out the precise path from point A in the retina to point A-prime in the base of the brain. CNS tissue doesn't regenerate very well.

  2. the transmitted image isn't a pixel map, but more a collection of motion and orientation vectors your brain assembles and learns to associate with, then recognize as, your mother's face. Learning at this level is a skill we lose in the first few years of childhood. Adult amblyopia is very hard to treat.

Given that we're cracking the code, given that there IS a pixel-type pattern of locations we can map in the visual cortex, it's more practical to project vision onto a mesh network of microelectrodes that make direct contact at the surface of the brain. Cybervision will happen before we can transplant/reconnect central nervous system tissue.

The skill necessary to "re-grow" vision will also enable monsters among us to create their own monsters.

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ozspook t1_j1ukd9m wrote

This kind of thing is enabled by the kind of 'robotic brain surgeon' microelectrode implantor that Neuralink is building.

So despite the mouthbreathers ranting about Elon implanting microchips in your head there is a lot of progress being made that will help a lot of people.

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Brain_Hawk t1_j1thr3n wrote

A full eye transplant would require detaching the retinal nerve and grafting it on to someone else, which is not currently a feasible form of technology. If we could perform those kind of nerve graphs, we could repair damaged spines and restore people who are paralyzed from spine severing. To the best of my knowledge this is still generally impossible.

The optic nerve carries information from different parts of the retina to the brain in a very specific way. This means essentially we would have to be able to one-to-one remap and reconnect nerves at the level of single axons, extremely microscopic it involving tens of thousands or hundreds of thousands of specific connections. It's not as simple as taking one nerve and then smashing it to another and hope they all link up. If we could get random events to link up together, the person receiving the eye transport plan would essentially receive White Noise Vision to their brain, with everything all mixed up and wrong.

We can currently do cornea transplants, and fun side bar, some recent advancement in transplanting retinal cells and restoring Vision when people have damage to the retina

https://www.mountsinai.org/about/newsroom/2021/scientists-take-important-step-toward-using-retinal-cell-transplants-to-treat-blindness

Personally I believe the widespread use of bionic style and implants, such as a robotic eye, will never become a big thing because the biology will outpace the engineering. So at least from a recovery of function perspective I don't think it'll take off. It's always possible that doesn't the form of human enhancement, for example producing biotic eyes that have different kinds of vision. But I think the biology will be a lot faster

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