Greetings Shooters,
The following topic may be of some benefit to our newer shooters. I was driving to work this morning and because of some mild allergies, I closed one of my eyes momentarily and for some strange reason, I was thinking "Bullseye!" (It's in my blood!)
I'm guilty of not shooting iron sights as much as I would like but nevertheless, I would like to share some of my recent experiences at the Hawaii State Championship. It appears that I missed a recent discussion on "Sights" with the Bullseye-l@lists.lava.net website while I was gone. I do not intend to teach my readers on how to shoot but I do know a thing or two about "Seeing." I've spoken to a few of you who have never made the President's 100 and yet are masters and are distinguished. It is my hope with this post to help some of you elevate your iron sight scores, ball and revolver.
Some of our newer shooters (and perhaps experienced crusty shooters as well) may close the eyelids of one eye while sighting with the opposite shooting eye. Generally, this is not recommended. We know that the pupil enlarges under dim lighting but many of us may not realize that if we squint to close one eye, the other open eye will dilate. This is known as a sympathetic response. With an enlarged pupil, focus tends to be worse as we discussed several times in the past.
Shooters using black occluders over the non-shooting eye will also get a similar dilated pupillary response to the shooting eye. However, a white occluder will elicit very little pupillary response of the opposite eye. A better choice would be to use a small piece of frosted scotch tape or equivalent on the center of the lens in front of the non-shooting eye, which many of our shooters prefer. This appears to cause the least pupillary effect to the shooting eye.
If possible, the best of all choices would be to keep both eyes open. I would encourage those who have not tried this, to do so. Have some fun as you experiment and be patient. As I was dry firing the night before the CMP EIC ball match and the Distinguished Revolver match, I made some important observations. I shoot dot sights with both eyes open but like many of you, I occlude my non-shooting eye for iron sights.
Seeing with two eyes is natural, seeing with one eye is not. Seeing with only the non-dominant eye requires more effort but many of you can shoot just fine this way. As I was dry firing, I looked at my homemade black bull which was placed across the room. I lined up my front and rear sights with a 6 0'clock hold while using different occluders. Vision was decent through my adjusted shooting Rx (you must have your best focus for the front sight). I must use these prescription shooting glasses for the iron sights because I am presbyopic like so many of you.
I then used both eyes without an occluder and as I aligned the sights to the bull, I saw two sets of sight images. This is called "Physiological Diplopia" and is normal. The left eye saw the right set of sight images. The right eye saw the left set of sight images. This is very important to remember. I'm left eye dominant and use my left eye as my shooting eye, so I need to align the RIGHT rear sight image along with the RIGHT front sight image and ignore the LEFT sight images. I was amazed with the clarity and stability of my sight alignment components while having both eyes opened. At this point, I thought I would try this way of seeing during the matches.
Many shooters have mentioned that the bull seems too blurry when focusing onto the front iron sight. The biggest advantage with keeping both eyes open is the improved overall vision as compared to single-eye vision. Quite often, eyes which are capable of seeing 20/20 will see 20/15 when both eyes are open. The second advantage would be to lessen the eyestrain whenever only one eye is used which leads to instability. "Sight Fading" due to the Troxler Effect is less pronounced when both eyes are open (during my own experimentation).
A rule of thumb we eye doctors use is that vision is reduced one line on the Snellen eyechart with every +0.25 diopter of power. Shooters who use a +0.75 diopter lens will see approximately 20/40 which is considered the minimum to pass the California Department of Motor Vehicle driver's license requirement. Therefore, the black bull does appear blurred and we may have a difficult time aligning the sights as well as we would like. With binocular vision, the two eyes not only see better, perhaps 20/30 or even 20/25 with the same shooting Rx, but also the vision is stable which is crucial in "exact sight alignment." I agree with those who have stated that proper sight alignment is the most important factor for obtaining a good shot. All else is secondary with iron sights. There could be a strong argument that proper trigger control would be right up there with sight alignment. Somehow with iron sights, I have found that the trigger pull comes naturally with proper sight alignment (Not so with dot sights).
I had put my dry firing experiment to the test the next day during the Hawaii State Championship. At 50 yards during slow fire, I had all the time in the world to work with my preferred sight images and ignored the second set of unwanted sight images. The trick was not to force my eyes to bring the doubled set of sight images together but to let them remain doubled and then concentrate only with the chosen set. Those who use the right eye to shoot, look only at the left sight images and those who use the left eye to shoot, look only at the right sight images. Occasionally, "Suppression" would occur and the unwanted second sight images would disappear.
With this way of seeing, I was hitting the black consistently at 50 yards. This gave me the edge for the leg points. I also tried shooting 50 yards while occluding the non-shooting eye during the matches which resulted in more hits on the white as vision tended to fluctuate a bit because my brain did not like the monocular vision. Again, binocular vision is more natural and results in clearer and more stable vision. The rest is up to you.
For the short line, I found that quick sight reacquisition was more important and found the occluder helpful, and at 25 yards, that big black bull was easier to see. I did not discuss the use of apertures with this article. Good luck with your quest whether it be the President's 100 or more leg points.
For more information on binocular vision for shooters, please refer to the "U.S. Army Marksmanship Unit, Pistol Marksmanship Training Guide, under Supplemental Information, Annex II. I went into more details and provided instructions. I have always maintained that advancing age was not a disadvantage, but rather, an advantage with irons.
Good Vision and Good Shooting To All,
Norman H. Wong, O.D.