Spinal injury? WHOOAAAA, NELLY! Can’t do anything about that. Sorry. Well, there is this new development. But seriously, it seems like we should’ve been able to do that in the 90s.
What took us so long? Why is it so hard to rehook what are essentially torn wires? Are they too small? Too fragile? Too numerous? Does they not “restart” once reattached? What held us back for so long?
Your sarcasm bothers me (if I read the “WHOOAAAA, NELLY!” that way). It bothers me because brilliant people aren’t just missing the obvious, and the world can’t wait to go, “DUH!, What were you mo-rons doing all this time?!”
I believe that is akin to this: Once the nerves are severed, you can plug 'em back together, but they don’t work. Complex biological reasons: Scarring occurs when cells called astrocytes converge on the injury, isolating it from surrounding tissue. Meanwhile, a dense meshwork of proteins forms around the injury, further sealing it off and interfering with regeneration.
The focus is to reverse or stop that now. Unfortunately, there is no bottle labeled “Use This” sitting around that contains a drug to make that happen.
Nerves are a lot more complex (not to mention often a lot smaller) than wires, and do not really do the same thing. The analogy is extremely rough.
Some of the other “cures” you mention do not work very satisfactorily anyway. A cochlear implant will certainly not provide anything like full, normal hearing. I do not know where you get “plastic retina” from, but even if such a thing a existed it would not cure cataracts. What you need for that is a plastic lens (and as someone who has two of those, I can tell you that although they are a lot better than having cataracts, they are nothing like as good as having a natural lens still in place).
A lot of editing of the OP. I was shooting for any eye treatment I could think of, and keratoprosthesis popped into my head. The ‘retina’ part was left over from the original ‘retinal treatment’ that was in the OP, but I couldn’t resurrect the right term (macular degeneration, btw) from my school days.
So yeah, let’s just sweep that under the rug. Move along, nothing to see (heh) here, folks.
Nerves are incredibly complex, with zillions* of microscopic connections made in patterns we don’t yet fully understand and that seem to be at least partially random. Each connection involves one tiny little chunk of cell membrane (defined in ways that, again, are not yet fully understood and certainly can not be replicated artificially…yet) maintaining a sort of “I’m not touching you! I’m not touching you!!” relationship to another tiny little chunk of cell membrane on the next cell down the line. These connections grow organically and have to be maintained by the cells in order for them to continue to function. Basically, the whole system is set up, run, and maintained by subcellular processes that are waaaaay to small for us to manipulate. At least so far.
With wires, it’s “make that chunk of copper touch this chunk of copper”. With nerve cells, a better analogy would be “let’s hook up these 47 peripherals to these 16 monitors and 88 sets of speakers, but all the connections have to be made inside a microscopic glass sphere by a blind man using only a pipe wrench”.
Now, there is progress being made, as in the link you provided. I’ve also seen reports of stem cells being injected into areas of spinal cord injury with some success, as the cells reproduce and integrate themselves into the gap, reestablishing connections. In both cases, though, researchers are essentially using the body’s own properties to heal itself (which is true of most medicine, actually) rather than going in and doing the rewiring by hand.
*zillions may or may not indicate a specific quantity