I would have to go shave to figure out how much I'm not seeing but I can tell you this, I shaved with my dominant hand for over a year. I was doing fine and every time I tried to switch to the left hand I would give up in short order.

I'd put the razor in my left hand, look in the mirror and get discombobulated and say the hell with it. Then Danny Wonderful posted that he learned to shave with the non dominant hand by practicing while watching TV.

So I did that for a few days and tried again. I got the same results when I looked in the mirror so I looked away. I felt the razor go where it was supposed to be and then looked and had no problem continuing the shave. Now I'm getting pretty good at shaving left handed and no longer get confused with placing the razor while looking.