Groo here
There in lies the key, your eyes don't adj.
The flash ,like a flashbulb, is too fast .
Your gun blocks the most intense part of the flash, at the muzzle,
something the target will see.
You get the "fringe".
The effect can been seen by shooting a camera flash at night.
The area will be lighted up for a short time ,you will "see" the area
and any targets as a quick flash- remember where they are and shoot there.
The flash from a gun will be longer lasting and easier to use.
The blinding most think of happens when you look AT the the flash.
That means from in front not when you look PAST the flash as when
you are behind.
Take your camera or real bright light out some night and try it.
We have all had pitchers taken so we know about the in front part.