I had this happen to me on several occasions. Once because I got a contact lens to protect a wounded eye. I told the doctor I could not imagine putting anything artifical in my eye while it is trying to heal. She insisted it would work for 80% of the patients. Once in, the world went black. It didnt even hurt. It was my brain refusing to accept this version of the multiverse. I make a point of mentioning my tendency to just pass out when I get slightly strange treatment from med personel. They seem to have it often enough, because they are always happy to hear in advance something might come up. Its strange, because I can not really predict if it will happen. I am not really afraid of pain. It is more like being afraid of loosing control or something.

Anyway, thanks for giving the phenomenon a name.