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Old guy eyes questions

16K views 65 replies 26 participants last post by  smoothy8500 
#1 ·
Spent some time on an indoor range today with mixed to poor results. Haven't really done any shooting for several years. Initially tried using simple shooting glasses. My usual prescription has a little magnification for distance but I regularly drive and work looking over the top of the lenses or without the glasses. I found that this didn't work at all well for either rifle or pistol. And was problematic when needing to switch to close use to open combo lock or read box labels, etc., on the line where swapping glasses when others were shooting could be dangerous and against range rules to be w/o eye protection.

Swapped back off line to my progressive lens bifocals and covered them with larger safety lenses. My usual glasses don't have great coverage even though they are polycarbonate so while the range attendant said, they'd have been acceptable, I don't think so. Plus, really poor results from the head angles needed and no help at all with the M1a.

Checking at home, single vision "computer glasses" seemed to work well for the pistol and the rifle. Have a scheduled yearly exam this weekend but was also thinking of starting with a pair of the dioptric glasses from http://shop.shootingsight.com/Safety-Shooting-Glasses-Shooting-Glasses.htm

I've seen several sources for approaching this with shooter bifocals, etc., with the correction in the upper or upper center. At this time, I don't need pistol corrections in daily wear but might want to consider that if I go for a CCW.

So besides, the single vision shooting glasses mentioned above, is there anything in particular I should ask the optometrist to check, or distances to check, recommendations for corrections to go with bifocal shooting glasses with a small alternative location on at least the right/dominant eye?
 
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#37 ·
Sounds like another fairly inexpensive and practical approach. Still waiting for a chance to try the new glasses in real shooting. Spoke with a classmate who is an optometrist at HS reunion the other night and he was immediately familiar with the .5 and .75 adds and he has worked with some shooters using them. He's thinking of trying to get a CCW but lives in the Bay Area (norcal) so admits it may be a difficult proposition.

Would a .625 work reasonably well going either way? Or is the lens "grind" set up limited to the larger steps?
 
#39 ·
The human eye can typically discern steps as small as 0.125, so stock lenses are available in 1/4 diopter steps, because any lesn will be within +/- 0.125 of where you need to be.

So even if you did measure out at needing a 0.625, if someone gave you a 0.75, it would be questionable if you could tell the difference.

That, plus I'm not sure your distance vision correction is constant. Blood sugar levels will change the refractive index of your eye, so your 'theoretical' focus will drift slightly during the day. Hydration level will change your eye diameter slightly as you inflate/deflate with liquids, which will change your focal point subtly. So in the end, I'm not sure that trying to measure to the nearest 1/8 diopter is truly a meaningful exercise.
 
#42 ·
I add a clip on pinhole device to my shooting glasses that increases the depth of focus.
Yes. THere are two elements to creating a good sight picture.

First, you want your eye to focus at a point that represents the average between focus on the target and focus on the sight. This will have the effect of centralizing your depth of field. You accomplish this by adjusting the lens power.

Second, you want your depth of field to be as big as possible. You accomplish this by using an aperture which is smaller than the pupil of your eye.

The aperture sight on the Garand was one of the factors that made it the greatest battle implement ever devised. Neither the German Mausers, nor the Japanese Arisakas had this feature, they all used V-notch sights, so the shooter's eye did not get the depth of field advantage.
 
#41 ·
Recently had cataract surgery on right eye, went back for check up with Doctor and now have 20/15 in the right eye. Scheduled to go back on April 7 for left eye procedure. I'll be 74 in March and it's a safe bet that those of you in late 50's or early 60's have the problem and quick eye check up will tell you, should have them checked out. Operation is a snap, takes something less than 30 minutes and painless. Just a suggestion.
 
#43 ·
Legally blind[can't drive no depth perception]since 19 months old. What helps me shoot better: Pistol: Old SWAT team trick: Black out the rear sights and acrylic paint the front sight post. I shoot much better now. For rifles, improved irons help me a lot, too. Hope this helps!
 
#45 ·
I've added stick on readers on my shooting glasses to help with aiming. You can place these where you want on your glasses (I put them on the top of the right lens) and it helps to focus on the front sight.

Just my $.02 on something that has helped me.
 
#47 ·
I've added stick on readers on my shooting glasses to help with aiming. You can place these where you want on your glasses (I put them on the top of the right lens) and it helps to focus on the front sight.

Just my $.02 on something that has helped me.
I'm gonna have to check these bad boys out!
 
#46 ·
I own a set of shooters glasses with the diopter at the top of the lens---Love them for pistol, (first time I have seen my front sight clearly in years)---but it does take practice to aim through the top of your glasses.
 
#48 ·
Problem is that most glasses to help you read are too strong to use for shooting. 'Reading glasses' range from about +1.25 diopters to +3.00 diopters. And yes, around +1.00 diopters will give you a very nice front sight, but it brings your focus in so close you lose the target. The entire basis of shooting vision that is different from reading correction that doctors understand is that you want to use the average of the correction for the target and the sight, so your depth of field is centered between the two, hence the correct solution of +0.50 for most rifles. This moves your focal point closer to, but not all the way, to the front sight, but also leaves some of your focus on the target.
 
#50 ·
I sell them. I worked with a safety glasses company and had +0.50 for rifle and +0.75 for pistol made.

To be clear, you want to add +0.50 or +0.75 to any distance prescription you have. If you have 20/20, you are good to go, and only need the +0.50 or +0.75, but if you do have a distance correction, even mild, you want to do the math and get custom lenses.
 
#58 ·
Just got back from spending a week at Camp Perry, where I shared a vendor's hut with Bob Jones, so I can confirm he is very much alive, just a little beat up. He leaves Camp Perry at the end of this week, heading to the Mayo Clinic to get two new knees installed. Also in the building was Alan Aronstein from Interarms/High Standard, and Ron Norton from Inland. I spent a lot of time talking optics for shooters while up there.

What struck me is how few people know what the definition of 'diopter' is when dealing with lenses. Diopter is simply the inverse of a lens focal length, in meters. Sounds complicated, but it isn't. If you focus your eyes at infinity, and I stick a 2 diopter lens in front of your eye, your focal point will now be at 1/2 meter. If I stick a 3 diopter in, you will focus at 1/3 meter. If you reduce it to an 'estimate', you can just assume 1 meter = 1 yard, so 2 diopters focuses you at 18" (good for reading), 3 diopters focuses you at 12" (remember the 12" rulers that went to 30cm on the other side?). If you use different powers, you might need to dust off your fraction math, but the concept is unchanged:

A 1 diopter lens will focus you at 1/1 = 1 meter.
A 1.5 diopter lens is 3/2 diopters, will focus at 2/3 meters. 24"
1.75 is 7/4 diopters, will focus at 4/7 meters. (OK, I need a calculator for that one)

Fractions work too: a 0.5 diopter lens is 1/2 diopters, and will focus at 2 meters. My 0.75 diopter glasses are 3/4 diopter, and will focus at 4/3 = 1.333 meters, = 48".

A zero diopter lens will put your focus at 1/0, which is infinity, which is where your eye was focused in the first place, so a zero diopter lens is no lens, it is just a plain piece of glass, and for people who need no correction in one eye (or just want to wear glasses to look cool), it is referred to as a 'plano' lens

Any positive diopter lens will move your focal point closer to you. But wait! There's more. You can also make NEGATIVE diopter lenses. They push your focus further away from you.

Here is the cool part: diopters add. If I stack a 1 diopter lens on top of a 2 diopter lens, it effectively becomes a 3 diopter lens. If I stack a +2 diopter lens on top of a -2 diopter lens, they cancel each other out. This is how eye glasses work. Your relaxed eye is SUPPOSED to focus at infinity. If you are near sighted, your relaxed eye is focused up close. So basically your eye has a +2 or +3 built in. Your distance vision prescription that lets you see to drive, will be a -2 or -3 lens, so the 'built in' power in your eye is cancelled by the eyeglasses.

For shooting, Diopters can also be averaged. If I want to centralize my focus between the sight and the target, which will in turn centralize my depth of field, I simply calculate the diopter needed to see the target perfectly, and the diopter needed to see the sight perfectly, and average those two values. If you have good (or corrected) distance vision, the diopter needed to see the target is effectively zero. A target that is 100 m away from you requires a 1/100 diopter lens = 0.01 diopters. The human eye cannot see changes in focus less than about 1/8 diopter, so a 0.01 diopter looks like a zero diopter to your eye. On a Garand, the front sight is about 34" from your eye, depending on head position and neck length, etc. 34" is 0.86 meters, so requires a 1 / 0.86 = 1.16 diopters to see perfectly. As a final step, we then average 0 diopters for the target with 1.16 diopters for the front sight, and arrive at an average of 0.58 diopters to centralize your depth of field on a Garand.

Lenses come in 1/4 diopter steps (and you typically want to round down), so 0.58 becomes 0.50, and that is where my recommendation for adding +0.5 to shoot the Garand.

Bringing this full circle - I said lenses add. So if you are near sighted, focusing at 1/2 meter (ie a +2.0 power 'built in' to your eye), the doctor would have prescribed you a -2.0 lens to see. But I want to 'add +0.5' to shoot the Garand. You could have in -2.0 contacts, then use my +0.5 safety glasses, or you could simply add the -2.0 and +0.5 and get a -1.5 lens in regular glasses and be in great shape.
 
#59 ·
You could have in -2.0 contacts, then use my +0.5 safety glasses, or you could simply add the -2.0 and +0.5 and get a -1.5 lens in regular glasses and be in great shape.
Good to know this about contacts and corrective glasses for shooting. I recently had a conversation with a couple shooters at a Garand match discussing my shooting glasses and the question if glasses and contacts could work together came up.
 
#60 ·
Absolutely. When I said lenses add, I meant both in the real sense, and in the mathematical sense. So, if you have -2 contacts and wear +0.50 glasses, you effectively have -1.50 correction, or else I can take your prescription for -2, and add +0.5 and prescribe a -1.5 lens. You can do that with contacts plus glasses, I also do it for people with corrective glasses, I sell clip-on +0.50 lenses that they physically clip on in front of their regular glasses lens.

Note that I have simplified this math; lens distance from your eye also plays a role, but usually for small shifts in distance, and when your lens power is pretty low to start with, this effect washes out in the rounding. When you get really strong glasses, like 5 diopter and up, it does make a difference, so math for those people is not quite as simple. Also match shooters, who take a 0.5 lens and put it in the front sight, so the distance is huge - math is different for them.
 
#61 ·
I can see distance pretty well, but use readers. Per Eye Master's advise I ordered two pair of safety glasses for range shooting: +.50 and +.75 for open sight shooting. Although not perfect, these really help. I have to cant the glasses to one side to get the clearest sight picture, but the improvement over no correction is noticeable.
 
#65 ·
My experience is that bringing up shooting likely confuses the eye doc, because they have never dealt with depth of field calculations. Best is to just get a standard 'distance' prescription, and then I can explain how to do the correct offset for shooting.

If you do want to have them attempt it, do not say that you want to see the front sight. Instead, make sure to explain that you need to see the front sight at the same time as the target, and so you need to focus at the 'hyperfocal' distance of the front sight. Again, in my experience, eye doctors do not like patients telling them how to do their job, so that may, or may not, help.
 
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