I quote myself from another thread here - Not directly 'on topic' but certainly relevant.
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I was mentioned here because this is what I do for a living. I work with brain injuries and developmental problems - dyslexia being one of these, and this is where one will find issues of poor or incomplete visual dominance.
First, a bit of science and 'who's who' - this is rather important in that what most people think of when they talk of 'visual dominance' has nothing to do with the neurology involved (I believe this is what gunfitter is trying to state in his posts - but I don't wish to put words in his mouth.).
Frank Rively and I have spoken on this a bit and I think we agree, albeit it we see it from different perspectives. I work with children with developmental problems that impact their whole lives negatively - from failure in school to being a cause for delinquency and crime. Dr. Rively comes at it from helping shooters add more targets to their score. We will tell you very different things, but we hold the same understanding of the problem. In fact Dr Rively is well known for his knowledge on the optometric extension program aspect of human visual dominance, something we helped to develop.
I also work with William Padula, who is perhaps the preeminent optometrist for visual field defects commonly referred to as 'visual mid-line shift.' This is typically the result of a trauma, but may develop on its own and again, it can impact ones (visual) life immensely.
These two will be my 'phone a friends.'
I have spoken to Phil Kiner about this and I think he understands what I am about to say. Also, I have gone over this with most of the people trained in the Dan Carlise school of shooting on this as well.
Now the science...
I'll start with the controversial part - visual dominance does NOT exist in the eyes - it is a neurological function of the brain - inclusive of neuronal pathways and the perceptual aspect of the cortex, and lower portions of the brain as well. As such anything one does to deal with this issue that involves only the eyes is a symptomological treatment at best. I include a graphic of the visual pathways - this shows how information is received, transmitted, and the perceptual areas involved in the brain. It speaks nothing of how we perceive visual stimuli.
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First thing to note here is that your eyes do not send a signal completely to one side of the brain or the other - the red and blue shaded areas show clearly that both eyes send a portion of the visual data to both hemispheres of the brain. The signals are 'equal' in scope, but they differ somewhat in that data they contain. For most people this is an odd thought, but if you understand the physics of how the eye works it makes perfect sense.
So, if both eyes project 'equally' to both hemispheres of the brain how can you have a 'dominant' eye? If you try to evaluate the map one might be correct to think that things in our right visual field would project to the left visual cortex - and we would be 'right eye dominant' in that situation. Reverse the parameters - with the object in the left visual field - with a projection to the right visual cortex and we would be best served to be 'left eye dominant.'
Hmmm, how then can we have visual dominance in one eye??
Now you need to look closely at the second diagram - look carefully at the back of each eye and you will see an area where the red shade and the blue shade overlap (highlighted in red boxes in the second image). This is the macula - the center of our visual fields. It has our most refined vision and it is what we rely on for our daily visual input most of the other portions of the visual field fall into what is colloquially called 'peripheral vision.' The macula provides our 'central vision' and it is really what we humans refer to when we talk about 'seeing' on a daily basis - this in fact is our source of 'daily vision.' This is what allows us to see fine detail, and is in fact what allows us to read and write.
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The maculas of each eye project fully and equally to both hemispheres of the brain. Remember, this is the portion of the eye we refer to when we are talking about 'sight' and 'seeing,' it is, in fact the source of our 'best quality' vision and what we truly rely on from day to day - it also is where we gain 'visual dominance.' But, with equal projection to both hemispheres the only way one can have a visual dominance is through a neurological function within the brain itself. The eyes do not matter, the pathways do not matter - only the brain - through perception, cognition, and action on the data - determines dominance. (NOTE: I have simplified this for clarity)
When someone speaks of being 'left eye dominant' or 'right eye dominant' they are referring to the same data within the brain for each eye. The dominance comes not from the eyes, but from how the brain perceives that data and the subsequent actions upon it. An odd thought, but a certainty owing to the science involved. (a more involved discussion can be found relative to this if one searches for 'macular sparing')
From where and how do we become dominant visually?
Borrowing from Robert Pirsig the best way to explain this is through an examination of the 'Quality' of vision - in terms of cognitive perception. Essentially our brains "see" the image projected from one "eye" as being the better of the two before it (it has more 'Quality'), so it relies primarily on that image. In a highly dominant person this disparity of Quality is large and hence they rely on only one 'eye' for most if not all of their primary visual input. If the quality is low - or near equal between the two 'eyes' problems of changing or shifting dominance can occur.
Don't worry - it gets even more complicated...
There is a neurological concept of 'laterality' that enters this discussion as well. Basically it states that if you are right handed you should be ALL right sided - relying on the right hand, right ear, right foot, right eye... If not (i.e., right handed but left eye dominant for our discussion) you are at risk for dyslexia and a host of developmental concerns. Oh, and poor shooting scores...
What does this all mean??
1) If you are 'well lateralized' with the dominant eye on the same side as your trigger finger you are basically good to go.
2) If you are 'well lateralized' with the dominant eye on the opposite side as your trigger finger you are going to have problems shooting and will have to find some adaptive process to shoot well. (Think of using 'Kentucky windage' when shooting a rifle where the scope is miss-aligned).
From a neurological/developmental point of view becoming a 'switch hitter' (switch shooter?) is a BAD idea.
3) If you are 'poorly lateralized' your shooting is going to suffer for a host of reasons. Solutions for these can be simple to very complex, depending on the specific nature of the specific issue involved. This is where the misunderstandings start...
Too many people want this to be a 'one size fits all' process - never has been, never will be.
The two things I see most often are these.
First, a person who is reasonably well dominant with one eye (ideally the eye on the same side as the trigger finger) - but not perfectly so. This person will, under specific conditions flip visual dominance and start missing shots. This typically occurs with fatigue or a specific lighting situation, but many things can impact this.
Second, the person with poor visual dominance starts out with this flipping visual dominance from the get-go.
What to do??
The first thing you should do if you suffer from this type of problem is try to evaluate under what circumstances/conditions cause you to have problems? This will take some intense reflection, even questioning people you shoot with frequently who observe your shooting can help. You goal is to gather as much information as you can. With that in hand you can approach a professional for help.
I would suggest you seek a specific type of doctor - an optometrist (NOT an ophthalmologist) with experience with the 'optemetric extension program.'
Some personal observations from the shooting line.
1) Gun fit really matters - especially if you have fragile visual dominance. Quite simply, the better the gun fits you the less dominance issues can raise their ugly heads. We as Americans pay little attention to this, in Europe it is where everyone starts. (I think gunfitter, in that he is in fact a gun fitter gets his fervor from this point).
2) Beads can be your worst enemy... If you have a fragile dominance a gun with beads may hurt your shooting. As you follow the target preparing to shoot your brain has a neurological pattern it expects to follow. If this is altered (i.e., if your dominance is in a fluxing state) your brain screams for more information, and one of the things you will do is verify the barrel location - and you check the beads - and you miss the target.
This sudden need for more visual data can be the origin of a 'flinch.'
How to solve this? Well, a big part is covered in number 1 above.
3) My 'pet peeve' is the concept of "muscle memory" because it does not and cannot exist. Yes, a consistent and repeatable pattern of movement can be created, but it involves neurological pathways (which control peripheral muscles) and the brain - the muscles are just the down stream target. What occurs in a 'muscle memory' process is that the actual nerve pathways become strengthened - nerve axons enlarge, neurotransmitters increase in concentration, receptor density increases, and perhaps most importantly, myelinization of pathways increases. The net result is that the nerve pathways become 'stronger' allowing for a better control of the down-stream muscle (per my earlier comment one could say the pathway increases in it's 'quality.')
Please do not misunderstand. This process (your 'muscle memory' - my reinforced neurological pathway) is important for being able to shoot well and consistently.
Food for thought.
