Eye Index aiming systems work because the pistol is between the eye and the target. How well those systems work and under what range of conditions is a legitimate debate.
Many believe Eye Indexing by its nature is not point shooting. I tend to agree. For the sake of argument I have included it in this series of posts. Whether you agree or not, I hope you will not get bogged down in semantics.
Hand/Eye coordination is something humans use very well. We use this coordination everyday to function. I like using the example of turning on a light switch. Reaching out and touching a small spot on the wall is not much different from reaching up and visually placing the front sight on that same spot. The analogy is that the finger and sight work in a similar way.
We have a high completion rate of turning on light switches. When you have failed to turn the light switch on what caused it? Did you not focus on the switch or not look at it at all? Did you move by the switch quickly and miss your target?
Think of turning that light switch on every day but as you walk up to it close your eyes. Now with practice I think you can turn it on. But I don’t think your success rate will be anywhere as close to how you usually do it, with your eyes open.
As a young child first learning to turn on that light switch do you think you would learn faster or slower if you always closed your eyes before trying to move your finger to the switch? Would it take longer to learn? Would you ever meet the same success rate you enjoy now with your eyes open?
It is my belief that your learning curve would be harder and longer if you never look at the switch or if you never see your finger as it moves to the switch. The proprioception and kinesthetic awareness required to turn on that light switch is the same awareness that allows you to place the front sight on target successfully. Using the hand/eye coordination allows that function to be better calibrated or learned to a finer degree.
Why I prefer to focus on my front sight before I press the trigger versus focusing on the target while I press? If you focus on your target and line up your front sight in between what you will see is at best a blurry front sight and at worse a ghost or double sight. Either way in my opinion this makes the front sight seem wider. This then makes it harder for me to center the wider sight on my target. Essentially I am making the relationship between sight and target closer to the same size. This is the same as using the width of the slide itself as a sight.
Using my light switch analogy doesn’t work as well here because it is easier to physically touch the switch with a fatter finger. But if I trade and use the analogy of making the switch smaller while keeping the finger size the same, you can see that it would be harder to manipulate a smaller switch.
The accuracy of each focus also depends on the shooters eye health. Some people have problems focusing at certain distances. Personally for my shooting and watching hundreds of others it is my belief that some misses occur by not transferring the focus to the front sight. For me that makes it more than worthwhile learning.