I used to swear by those little "Third Eye", eyeglass mirrors, since I ride with music sometimes. Plus I just like to be able to see what's coming up from behind without having to turn.
Late in the season last year I began to have a lot of neck pain and pinched nerve feeling in my neck and back on my left side. Eventually it got pretty severe and I was in a lot of pain for a month or so. Over the winter it has gradually subsided and now it's pretty much gone, but it was pretty bad for awhile. I've been riding over the winter but I haven't been using those mirrors anymore, because when the pain was bad I couldn't move my neck much.
Anyways, I've been riding quite a bit for the last month or so and it dawned on me that it might have been the constant movement from checking that rear view mirror that caused, or at least contributed to, the injury. Now I have a small bar end mirror, and instead of moving my head up and to the left to check what's behind, now I just have to swivel my eyes a little bit down and to the left, which seems to be a much more natural movement.
Somewhere I read that the optic nerve in your eyes are connected to the nerves in your neck and back and blah, blah, medical science and all that confusing crap. But the concept that the constant repetitive movement of your eyes and neck muscles in one direction could cause an injury makes some sense.
I was just wondering if anyone else has experienced anything like neck pain, pinched nerves, etc. from having either eyeglass or helmet mounted mini-mirrors?