> The retina does not respond to the 905-nm infrared light used in current car lidars, so we can’t see it. But the eye transmits 905 nm to the retina, so it’s subject to the same restrictions as visible light. In fact, it’s even more hazardous because the eye cannot automatically turn away from a bright source that the retina can’t sense.
The eye is opaque to 1550 nm light, and so even if you are looking right at it none of it makes it to the retina.
Which isn't to say that 1550 nm light is safer -- the mode of destruction is just different, e.g. corneal damage leading to cataracts or surface burns rather than retinal damage.
As I understand it, it’s largely a focusing issue. Close to the visible range, a distant point source gets focused to a point on the retina. At 1550nm, the energy is deposited uniformly on the cornea unless the laser is focused to a tiny spot on the cornea.
edit: I don’t know to what extent this is relevant, but humans can regenerate the corneal epithelium. Think about all the sand you’ve gotten in your eye as a kid, and the fact that it probably didn’t accumulate enough damage to blind you.
I'm still reading it, so I can't tl;dr it quite yet, but the answer in theory should be in here.