Every instructor has run into this at one time or another. Usually one student per class, but sometimes we get lucky and only see it everyother class or so. Invariably it starts with a student that just doesn't seem to "get it", or is slow catching on to the basics. Many times it can be directly related to an eye dominance problem...usually CROSS dominance, where the dominant eye is on the opposite side of the strong hand. The instructor will hear things like it all looks fuzzy, or I see two of everything unless I close an eye, I can't focus on the sight and even see the target. Usually it takes a bit of one on one to figure it out and either have them use their dominant eye to aim with or dim their dominant ey so they can shoot with their "strong" hand....Now all this is well and good for a pistol, but what do we do with a rifle, and how does dominance effect our ability to use one fast and accurately.
We will take the worse case first. Strong off-side dominance and inability to use weakside shooting. The shooter just can't seem to figure out how to get comfortable shooting off their weak side in order to use their dominant eye. This shooter will need an optic that glows brightly AND has the ability for magnification A good 1-4X scope that is daylight visible. The dot allows the non-dominant eye "see the aiming point" and the magnification will allow the weak eye to see the target magnified in the same focal plain as the dot, at distances exceeding 50 yards. In general their transitions will be a bit slow unless they Prairie Dog their head while transitioning from target to target ( pop the head up above the scope to index on the next target). For this person IRON SIGHTS ARE IMPOSSIBLE TO USE!
Next we have the strong side dominance and strong side shooter. Easier to train as he isn't fighting a focal problem, but the short coming is that transitions one way or the other will be slower, due to the fact that the off-side eye is really just along for the ride. Red dots and scopes work well for them, but as magnification increases so does the propensity for "getting stuck in the scope", as they don't have the ability to focus on anything specific with their off-side eye. This shooter will say things like "only a red dot is fast up close", "Any magnification is bad when shooting at less than 50 yards". Transitions will be fairly fast one way and not the other, and if forced to transition the other way will almost always resort to Prairie Dogging. This shooter can use most sighting system fairly well and will be able to utilize iron sights to a fair degree of precission, but will find them slow when shooting in the 0-50 yard range as their eye will be focused on the sight and it will have a bit of focal trouble "seeing the target" and putting all of it together for a fast shot, because his off-side eye isn't helping him.
Next, the shooter who isn't stongly eye dominant or has no dominant eye, about 15% of shooters fall into this catagory. In general they will be able to use any type of sighting system fairly well and at almost any magnification from 4-6X on down ( magnification higher than that will almost always cause the magnified image to "take over" in the image their brain chooses to see ( non dominance allows the shooter to decide mili-second by mili-second which image, from which eye it CHOOSES to see). Examples of these types of people are Glyn Bindon (Trijicon inventor and proponent of the Bindon aiming concept). Dale Armsen of the "occluded gun sight" fame. This shooter can use a low powered scope or dot with equal ease and won't be able to figure out why everyone else CAN'T....This should be a big warning to instructors!! If an instructor ISN'T eye dominant and doesn't know about this he will NEVER understand why some of his student can't do this stuff!!.
This shooter will almost always be the fastest with iron sights in close to mid range (around 150 yards), BECAUSE there is no scope to block his vision one way or the other for either eye, it is easy for him to "see the target" and a sharp clear sight picture, and ALL the open space around it for as far as his perriferal vision extends. He will not need to Prairie Dog as his eyes can see his next target because they can almost work independently (think Iguana vision). A bright dot will tend to draw his eye away from what he usually sees and will in fact slow him down a tiny bit, unless it is very dim!
So in closing, if you are instructing and you have a student that "just doesn't get it" you might take the time to find out if it is eye related. In general most shooters are going to do better with glowing dots and low powered optics that glow for any kind of "tactical" rifle class due to eye dominance issues. There are varring degress between these 3 I have outlined, but in general you will be better off with a dot or low powered variable optic
We will take the worse case first. Strong off-side dominance and inability to use weakside shooting. The shooter just can't seem to figure out how to get comfortable shooting off their weak side in order to use their dominant eye. This shooter will need an optic that glows brightly AND has the ability for magnification A good 1-4X scope that is daylight visible. The dot allows the non-dominant eye "see the aiming point" and the magnification will allow the weak eye to see the target magnified in the same focal plain as the dot, at distances exceeding 50 yards. In general their transitions will be a bit slow unless they Prairie Dog their head while transitioning from target to target ( pop the head up above the scope to index on the next target). For this person IRON SIGHTS ARE IMPOSSIBLE TO USE!
Next we have the strong side dominance and strong side shooter. Easier to train as he isn't fighting a focal problem, but the short coming is that transitions one way or the other will be slower, due to the fact that the off-side eye is really just along for the ride. Red dots and scopes work well for them, but as magnification increases so does the propensity for "getting stuck in the scope", as they don't have the ability to focus on anything specific with their off-side eye. This shooter will say things like "only a red dot is fast up close", "Any magnification is bad when shooting at less than 50 yards". Transitions will be fairly fast one way and not the other, and if forced to transition the other way will almost always resort to Prairie Dogging. This shooter can use most sighting system fairly well and will be able to utilize iron sights to a fair degree of precission, but will find them slow when shooting in the 0-50 yard range as their eye will be focused on the sight and it will have a bit of focal trouble "seeing the target" and putting all of it together for a fast shot, because his off-side eye isn't helping him.
Next, the shooter who isn't stongly eye dominant or has no dominant eye, about 15% of shooters fall into this catagory. In general they will be able to use any type of sighting system fairly well and at almost any magnification from 4-6X on down ( magnification higher than that will almost always cause the magnified image to "take over" in the image their brain chooses to see ( non dominance allows the shooter to decide mili-second by mili-second which image, from which eye it CHOOSES to see). Examples of these types of people are Glyn Bindon (Trijicon inventor and proponent of the Bindon aiming concept). Dale Armsen of the "occluded gun sight" fame. This shooter can use a low powered scope or dot with equal ease and won't be able to figure out why everyone else CAN'T....This should be a big warning to instructors!! If an instructor ISN'T eye dominant and doesn't know about this he will NEVER understand why some of his student can't do this stuff!!.
This shooter will almost always be the fastest with iron sights in close to mid range (around 150 yards), BECAUSE there is no scope to block his vision one way or the other for either eye, it is easy for him to "see the target" and a sharp clear sight picture, and ALL the open space around it for as far as his perriferal vision extends. He will not need to Prairie Dog as his eyes can see his next target because they can almost work independently (think Iguana vision). A bright dot will tend to draw his eye away from what he usually sees and will in fact slow him down a tiny bit, unless it is very dim!
So in closing, if you are instructing and you have a student that "just doesn't get it" you might take the time to find out if it is eye related. In general most shooters are going to do better with glowing dots and low powered optics that glow for any kind of "tactical" rifle class due to eye dominance issues. There are varring degress between these 3 I have outlined, but in general you will be better off with a dot or low powered variable optic
The prairie dogging comes into play and works sometimes, sometimes not. 
