So the short TLDR answer is that they are only working on one part of this. There are 30+ teams who were awarded funding and are working on the THEA project across the US [1]. Those teams are each working on aspects of one of the three different technical areas. Those technical areas are:
TA1: Retrieval of donor eyes and tissue preservation
TA2: Optic nerve repair and regeneration
TA3: Surgical procedures, post-operative care, and functional assessment
So this is very much a divide and conquer problem and no one team is planning to just figure out the whole solution. They are all still very ambitious projects but they are targeting much more discrete problems and working with other relevant teams on the project to bridge the gaps between their specific projects. To get a better idea of how it all ties together you probably want to skim through their proposers day presentation [2].
The issues I am talking about are all TA2, so the breakdown doesn't help. It's just a completely different technology readiness level.
Edit: Just looked at the video. There is ONE THIRD OF A SLIDE described for less than 90 seconds (28:27) that addresses the issues I raise. They just list random things people might try like "stem cells". Just bizarre
I have downgraded my respect for ARPA-H. Hopefully this is just some fluke to have gotten approved.
I was linking the proposers day video not as a direct answer but rather to try and show how that specific aspect is connected to all the other research going on on this topic as well.
And they even mentioned in that video that TA2 is the particularly hard problem.
And to address your question I linked the teaming page which does go into what the teams are pursuing to solve that problem. One of the teams addressing the specific issue you brought up is the USC team. They are developing electric field stimulus systems to drive regeneration of optic nerves along with real time imaging/monitoring equipment so that they can control said stimulus to drive regeneration along the paths they want.
TA2 is very big/broad and a lot of different teams are taking quite different approaches at how to address aspects of TA2.
It is likely going to be possible to grow an eye in a vat.
I talked to a retinologist who was working on genetic diseases like retinitis pigmentosa and he mentioned that in the lab their stem cell developments were growing not only retinal cells but at least malformed somewhat recognisable eye structures.
I fully believe that at some point in the next 50 years full organ replacements from the patients own stem cells (perhaps with lightly edited genetics) will be commonplace.
TA1: Retrieval of donor eyes and tissue preservation
TA2: Optic nerve repair and regeneration
TA3: Surgical procedures, post-operative care, and functional assessment
So this is very much a divide and conquer problem and no one team is planning to just figure out the whole solution. They are all still very ambitious projects but they are targeting much more discrete problems and working with other relevant teams on the project to bridge the gaps between their specific projects. To get a better idea of how it all ties together you probably want to skim through their proposers day presentation [2].
1. https://arpa-h.gov/research-and-funding/programs/thea/teamin...
2. https://www.youtube.com/watch?v=fRNpeU8_RLo