From: ke4zv!gary@gatech.edu (Gary Coffman)
Newsgroups: rec.guns
Subject: Re: Sight picture and eyes
Date: 8 Oct 92 17:42:07 GMT
Organization: Gannett Technologies Group

In article <9210020511.AA07933@hpfcpp.fc.hp.com> davep@hpfcpp.fc.hp.com (David Post) writes:
#I wonder what is going on with my eyes.
#
#The past few trips to the range I have noticed the my dominant eye doesn't
#seem so dominant anymore.
#
#I seem to focus on the handgun's front sight ok, but often there are two
#target images.  I don't exactly need to work to make sure I have the right
#target, but it is distracting.  It is especially bad when there is motion in
#my field of vision.
#
#When I lower the handgun and my focus shifts to the target, I see one
#target.
#
#I'm not so sure what I am observing is abnormal, but something has changed.
#Has anyone else noticed this?

Welcome to middle age. :-(

You are becoming progressively far sighted as you age. Eventually even
single vision glasses can't solve the problem. The technical term for
what you are experiencing is called "afterimage." To those of us to whom
this usage seems strange, the optometrists say "So what, it's our business,
we'll call it what we want." :-(

A young person can rapidly shift focus from near to far. The shift is
so rapid that both the sights and the target seem in focus at once. As
we age, our ability to rapidly change focus declines, and we start to
let the target fuzz out while keeping the sights sharp. As we age more,
and we get more far sighted, we start to see the double image. What we
are really seeing is a double reflection in the lens of the eye as it
goes further out of shape trying to compensate for increased farsightedness. 
It's usually worst in low light. If you start seeing doubled street lights
at night, you've got the problem. The tipoff that you have this condition 
and not an eye dominance problem is that closing one eye won't make it go 
away. You may not have this problem all the time, only after you have 
concentrated on something fairly nearby for a while, like a computer screen, 
or when your blood sugar is low. It will continue to get worse, however.

The solution is, brace yourself now, *trifocal* lenses. Find an optometrist
who will work with you, bring in your pistol, check that it is unloaded,
check it again, now show the doctor that it's unloaded, and let him measure
where the sights fall in your visual field when you are in normal firing
stance. Have him measure the distance from your shooting eye to the front
sight. He can then make up a pair of trifocals with the proper perscription
in the middle lens to bring the front sight in focus. He will position
that lens so that the line between it and your distance perscription falls
exactly along the top of the sight. Your scores will jump back up where
they belong.

Or, you can put an Aimpoint or scope on the damn gun and forget about
it. With iron sights though, the trifocals are a must. They look a bit 
funny because my natural shooting stance is with my head tilted to the 
right. That makes the line run at a diagonal on the special lens when 
my head is upright. Expect to pay about $400 for this setup.

If you have *really* short arms, the problem could be eye dominance.
If closing the off eye makes it go away, then just learn to shoot
that way. However, since it seems to have come on recently, I expect
it's afterimage.

Gary