Peri-orbital Abrasions

[Dane Dormio]

Regarding the phenomenon of "peri-orbital abrasions": supposedly these are fingernail scratches around the outside of the orbit of the eye socket sometimes found on the faces of murderers who have killed by strangulation.  An explanation sometimes proferred is that the victim, while able to reach the assailant's eyes with his/her fingers, for whatever reason (presumably either ignorance or unwillingness) failed to actually penetrate the eye socket and damage the eyeball, thus possibly surviving the attack.

I have heard this phenomenon cited as reason for training in deadly martial arts, so that you won't hesitate or freeze when your life is on the line.  Does anybody have any references or anecdotes that can support/refute this explanation?