Better yet, try with both eyes closed. When I think I have alignment issues, often I'll set up a very long, straight-in shot. I'll take my stance, get down on the ball, take a few practice strokes..... then turn my head 90 degrees to the right and shoot.
Believe it or not, i make it most of the time. Thus, my alignment is correct, my stroke is straight, and the reasons I am missing have nothing to do with any of that; I'm either jumping up, "steering" my cuetip, poking the ball, or too worried about missing.