I have used a bar-end mounted mirror for about one high-mileage year in the past, and have for the last year switched to helmet mounted.
I will not consider the merit of handlebar vs. helmet mounted in detail, but I can say I would never have used the handlebar mounted one in the first place, if I knew how much, MUCH better, by so much far, the helmet mounted ones are.
I have considered your safety question some times, but honestly, in the event of a real fall with head hitting the ground, there are so much more sources of injury than the mirror (most of them are from the bike itself), that I prefer to just forget about it as a "hypothetical, unfounded fear".
That said, my mirror is a cheap, round, flat glass mirror one, those you buy for one dollar, with two plastic hinges. A friend of mine "convinced" me to use it, and he attached the mirror himself, with zip ties, to drilled holes on the helmet cap. Here it is:
The final result is ugly, I know, but it works incredibly well with no issues so far. And the helmet (the only one I have) is itself a beater.
Now regarding SAFETY, when I take a look at the picture you posted, and considering my current experience, I think:
- That metal wire REALLY feels dangerous. It's a thin, penetrating METAL part instead of a blunt, bulky, round-tipped plastic shaft.
- The mirror itself is a tiny piece of glass. It doesn't even have to shatter to fit inside the eye orbit.
- The whole system contains only very hard and damaging materials. No bulky plastic "paddings".
One important difference between "mine" and "yours" is that "mine" is a helmet mounted mirror, and "yours" is a glasses-mounted one. The former stays further from the eye itself, so it needs to have a wider glass to provide a good viewing angle. The glasses mounted one can be smaller, and needs to be lighter to be comfortable.
I think each one is a matter of personal preference, and in either case the very real and sure benefits far outweight the hypothesized risk, but using a helmed-mounted mirror is helpful if you have one helmet but a lot of glasses, and I think it is better to have the extra weight supported by the whole helmet/head interface than only by the glasses/head interface (that is, only the nose and the ears).
Hope this helps!