a) The chemical put into the retina is surprisingly biocompatible, in that it does not appear to have caused anything out of the ordinary to happen. It works by effectively converting IR light to visible light - so it does not involve ‘sending more data’ to the brain, or ‘opening another colour band’ or anything like that. It is seen as just plain old green light, because the crystal structure of the chemical basically converts 980nm~ IR to 500~nm visible green light. So no uber-neurohacking going on here.
b) The procedure they are using to put the chemical in place is fairly run-of-the-mill medical procedure for humans for treatment of eye diseases, albeit a little icky.
So, I’m surprised, to say the least, but this could actually work with humans as a fairly harmless enhancement. I’m still waiting for the other shoe to drop, but haven’t seen one in the study itself for the time being. (Disclosure: not an expert, but I follow related fields)
That's not so obvious to me. If this chemical were uniformly spread across the retina, then I'd agree. But if it's sufficiently clumpy, or ideally attached to every second green-sensitive cone, then it absolutely would give (N+1)-colour vision (N=3 in humans). On first glance I can't figure out what the paper has to say about this distribution... and even if it were uniform in their mice, perhaps the next step would be to make it non-uniform somehow.
The earlier way to do something similar was by genetically altering some cells, . If you inject a virus (carrying the modification) at a low concentration, then you do get just half the cells. Then the brain learns (in a few weeks) which cells are now giving what information, and you get more colours.  did this in monkeys, IIRC they are N=2 and the virus added the gene for one of the human receptors. I don't think it was safe enough for humans.
I don't think you are born with different wiring to the three different kinds of cones, your brain just learns to lump all the red ones together, so that a red object stays the same colour in different parts of your visual field. The claim is that the monkeys learned which of the previously-identical cones now had a new colour.
Do they lose any sleep philosophising about how these new colours are possible, and what to call them? Who knows. But I believe they can still do all the usual monkey things.
That's the point they can not distinguish more colors. Their retinal cones still have the same spectral response. They cannot distinguish between a normal 500nm green leaf and a 900nm infrared source.
The monkeys are in a different study, the one I linked a few posts above.
The nanoparticles sound to me like they could be safer? Would be interesting to know whether they can be non-uniformly spread, so that only half the green cones can see one.
Given that, and the tactical advantage of seeing NIR in low light situations, someone is going to try this on people. And the results of that study could have a lot of impact.
I was thinking this was cool because if it works in the cornea, it could possibly be injected into a contact lens and achieve the same effect. But it looks like that won't work because the effect depends on the chemical being in (very) close proximity to photoreceptors in the retina.
She didn't tell her boss because she had disabled the safety switch, for some reason that seemed good at the time.
"A process in which two photons with the same frequency interact with a nonlinear material, are "combined", and generate a new photon with twice the energy of the initial photons. In some cases, almost 100% of the light energy can be converted to the second harmonic frequency. These cases typically involving intense pulsed laser beams passing through large crystals, and careful alignment to obtain phase matching. In other cases, like second harmonic imaging microscopy, only a tiny fraction of the light energy is converted to the second harmonic."
Are there situations where you'd run into lights that are intrusively (or even blindingly) bright in IR but not visible wavelengths?
Edit: looking at the emission charts, it's a wider bandwidth than I expected, not sure how well the brain would be able to use the specificity of the green.
Things that are normally just cool enough to not emit significant visible would suddenly be visible. It's far far from the standard 7-14um thermal IR, but would be... well.. downright awesome.
It might be possible to design a mixture of these to generate "impossible colors".
Since they just convert light between frequencies, they won't show you any colors you couldn't see by illuminating your retina with the output frequencies the old fashioned way.
 -- https://www.physiology.org/doi/abs/10.1152/ajplegacy.1938.12...
 -- https://petapixel.com/2014/08/23/dietary-experiment-successf...
 -- https://petapixel.com/2014/08/25/retinal-neuroscientists-reb...
As most of the biology stuff went over my head, I couldn't find if it is reversible though, they just mention it was "stable" at 10 weeks after injection, but is it expected to be working indefinitely? Can you wash it out somehow, if you later decide against it?
What's the effect of giving more information to the cells, would the brain use the extra information to self improve vision? In my case the right eye would be used for training the left one.
Another experiment I am thinking of, If a 3 month old child suffer a retina detachment, would his brain be able to recover the full vision by the brain making appropriate changes?
"Gentlemen, we can rebuild him. We have the technology. We have the capability to make the world's first bionic man. Steve Austin will be that man. Better than he was before. Better...stronger...faster."
Your brain would essentially be forced to constantly process more visual data than it was used to... more data than human brains in general had evolved to process.
Surely that has consequences.
The other classic is "reverse vision" glasses that flip everything upside down. Takes about 2-6 weeks to rewire your brain, then everything appears normal... until you take them off.
Physiologically speaking, maybe the excess biochemical signaling could lead to fatigued pathways, chemical exhaust toxicity, cell death... but I think that could be overcome with a control plane that permits deactivation, so that you only use it selectively, and that passes the buck, leaving the burden of responsibility with the patient.
In practical use, I think subtle social consequences are a bigger accident waiting to happen, worth more attention than the subsequent, resulting inner well being (or lack thereof) of the post-op recipient.
Little things like having the ability to observe otherwise silent flatulence, notice residual keyboard heat, see through clothing, and perhaps even walls, watching dinner cook, that sort of thing would change the sense of self, sure. If it’s truly harmless, you’ll see an alarming level of adoption.
But it’s the arms race of being left behind, when seemingly the rest of the world gets something like this, and you can’t jump on the bandwagon, leading to an absurd amount of dangerous elective procedures that would likely become the bigger evil.
Suddenly ordinary just isn’t good enough, so what happens next?
If this did work in people, I would let a few waves of early adopters go first. It's a big open question as to how confusing things might be if you were IR/green colorblind.
Another part of me is more thinking "I wonder what unexpected side effects we'll see when we have data from clinically controlled trials of large numbers of people using this technology over timespans of 40-50 years?"
I was an early adopter of a simple sort of body modification - I had a small neodymium disc magnet sheathed in some inert material implanted in a finger.
It was cool and all, but I eventually got it removed because it was sensitive and if the inert sheath ever broke, it'd be bad news. Bodies don't like rare earth metals.
When I got it removed, the person who did it turned out to know the one who put it in (small world), and they told me that the new ones were tiny slivers which were almost impossible to feel, much less remove.
And that wasn't exactly comforting. Mine practically popped out, but a tiny sliver?
Nowadays, I think two or three times about those sorts of 'life hacks'.
No thanks. Not now, not ever.
one thing i wonder, is what happens when you sleep
But the two eye solution is interesting.
I bet you could also do palette swaps for everything
But if we could "see all wavelengths", for any reasonable definition of "see", that would imply our eyes and brains had evolved to distinguish visual signal from noise.