Ok. here is an idea.
Take a laser level, sit it on short rail at diamond one, and shoot it across the table to far pocket (kiddy corner) till the beam hits the back center of pocket.
Mark the table about 2 1/2 diamonds away from the pocket.
Mark the table about 1 1/2 diamonds from the rail with the laser level.
Set a OB on spot near pocket.
Set CB on spot near rail.
You are now on an exact straight line.
Approach the shot from behind but don't bend down.
Just look at it
Move your head back and forth to see when it looks like. (OB, CB and Pocket) As you move a little right or left it will NOT look very straight.
Once you get a good look at DEAD center in the pocket (OB, CB, and Pocket) then this is your "spot". This is where your eyes NEED to be.
Now get down into your shooting stance and see where your "eyes" fall. You might wanna have someone hold a mirror for you at this point, or you can just check your cue and use that as a guide to where your chin kinda sits above your cue.
Some folks are right or left eye dominant but I believe that we all do NOT line up the same even if two folks are right eye dominant.
For some reason, I line up more under my left eye than my right though I am right eye dominant. And it only looks straight to me in that position. If I line up between my eyes or under my right eye, the path does not look straight.
I think baseball has "punished me" because I batted right handed and thus my left eye was the eye that was getting the best view of the pitcher for the last 40 years of playing hard ball. My left eye thinks it is playing baseball when I'm playing pool, and it likes to "see" a certain way. Thus, I give my "brain" what it wants.
It is sorta like when you "look" at the table before a shot. You should do it in a standing position looking down. As humans, we have been conditioned to walk while looking at a downward angle.... if we looked straight ahead we would look like robots,and we would trip over everything and hit edges of tables. I'm sure our ancestors had to avoid various meat eating creatures lurking in the weeds in order to survive as well, not to mention snakes, banana peels, curbs, etc. etc.
Thus, we give our brain what it has been conditioned for during the last "few" thousand years or so. Same thing with getting our eyes right. Some folks will be the same, some won't. But you will need to find out what your natural "sighting" is for you so you can begin lining up every shot in the same way...... without it you will never be consistent.......
Obvious, there are some folks that have figured this out either on their own through trial and error, and even a select few that when they picked up their first cue it was already on the "right" path just by happenstance.