I think this wiki article (Beware: this is a bit gruesome if you're squeamish) on Anatoli Bugorski, who suffered a dreadful accident at the Soviet U-70 collider, might help answer your questions. A proton beam passed through his head.
He apparently saw a flash of light brighter than a thousand suns, but lived to tell the tale.
As for the physics of what Burgorski saw, I guess it was synchrotron radiation from the accelerating protons. The U-70 operated at energies of $70 $ GeV; the LHC in its first phase operated at $7$ TeV $= 100 \times 70$ GeV. Maybe you can do the synchrotron radiation calculation of LHC versus U-70 to see how much brighter the flash would be at the LHC.
EDIT: It's not clear whether the flash Burgorski saw was the result of light in his eyes, a psychological reaction of fright, or a neurological reaction from the protons stimulating his brain.