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View Full Version : Red dot sights and astigmatism



DevDoc
04-20-2014, 09:38 PM
Does anyone know why people with astigmatism(corrected, mind you) see red dot sights as stars, groups of dots, and or blobs of circles? Is there a similar type of sight which will work for me besides iron sights and traditional scopes?

Budget
04-21-2014, 06:05 AM
I admit I have no experience (good problem to have, very thankful for my eyesight) but I have read that the single dot red dots, IE Aimpoint, Trijicon, etc. are much easier to use than holographic sights, such as the Eotech.

Have you ever had experience with illuminated scopes? There are dozens of great options if you can see those clearly. ACOG, Elcan, to name a couple. What rifle is this going on, will it be AR or something a little bigger? Again, many options, but you're going to have to try out a few. I'd go to a gun show and try to look through as many as possible to see what fits your needs best.

DevDoc
04-21-2014, 06:17 AM
Thanks for the advice. It will be going on a yet to be purchased AR. I originally was trying to outfit my mini 14 but it(the mini) did not work well for my wife(we both shoot), so we are looking for a bit lighter AR and a scope to match.

MI-1911
04-21-2014, 06:39 AM
Cataracts possibly?

DevDoc
04-21-2014, 06:48 AM
I sure hope not. I was just examined a week ago and I am in my early 40s. Hadn't thought of that one.

MI-1911
04-21-2014, 06:58 AM
I sure hope not. I was just examined a week ago and I am in my early 40s. Hadn't thought of that one.

They're not just brought on by old age. Medications and other factors can cause them. Do you have trouble at night, especially when it's raining, and looking at street lights, head lights, etc? Did you see an optometrist, or an ophthalmologist?

pkuptruck
04-21-2014, 09:17 AM
cataracks?? sigh..

astigmatism is a deformity ( for lack of a better description) of the cornea.. thats WHY you see stars, blobs, etc..
it can be somewhat corrected by hard contacts, etc.. or major surgery...

just dont use a red dot.. I have the same issue, and unless I'm shooting someone elses gun with a red dot on it.. I dont..

Illuminated scopes are a little better.. less smearing of the image... ( better scopes.. not "cheapies" )

TomE
04-21-2014, 09:40 AM
cataracks?? sigh..

astigmatism is a deformity ( for lack of a better description) of the cornea.. thats WHY you see stars, blobs, etc..
it can be somewhat corrected by hard contacts, etc.. or major surgery...

just dont use a red dot.. I have the same issue, and unless I'm shooting someone elses gun with a red dot on it.. I dont..

Illuminated scopes are a little better.. less smearing of the image... ( better scopes.. not "cheapies" )
I got rid of 3 RDS because all I saw was a blurry dot. My 3rd SPARC shows a comma, which my friend with glasses didn't see at all.I returned 2 SPARCS before this one.

DevDoc
04-21-2014, 11:51 AM
I took a picture with my camera and all of them looked perfect. I just thought I had bought junk. Whoops. I think I can see out of prismatic scopes. I don't know if that is just a fancy name for illuminated regular scope but I can see with them. Any thoughts?

solarguy
04-21-2014, 12:24 PM
1. The highly monochromatic light from an LED really emphasizes astigmatic error. You might look at a red LED clock in dim illumination and notice the halos as well.

2. If your astigmatism is very well corrected, it helps. However, there are impediments to that. In glasses, the best optics are at the optical center. When they make glasses for you, they measure your "PD", which stands for inter Pupillary Distance. That puts the optical sweet spot (the optical center) right in front of your pupil. However, that assumes your eye and your head are all looking dead straight ahead. When many shooters get up in the shooting position on a rifle, they are NOT looking through the optical center.

And if you wear progressives, this phenomenon is much worse as you get away from the OC. Very common among those over 40...

3. What lens material? Polycarbonate, which has other wonderful properties, has the worse chromatic aberration, which will make the halos/starbursts worse.

4. How big are your pupils? This varies a lot. Big pupils makes it much worse. Many medications will make your pupils bigger. Is it dim illumination? Yup, that makes your pupils dilate, making the problem appear worse.

5. Are your eyelashes in the way? Some folks have long eyelashes, and it's virtually impossible for them to look through an optic, without looking right through the tangle of long curly eyelashes. Yes, that makes it worse. Similar problem if you have droopy eyelids that start to impinge on the pupil area, ditto if you like to squint when you look through an optic.


hope that clears up some of the mystery.

Yes, I'm an eye doctor and yes I'm a shooter. I know -exactly- what you are going through.

troy

MI-1911
04-21-2014, 01:13 PM
3. What lens material? Polycarbonate, which has other wonderful properties, has the worse chromatic aberration, which will make the halos/starbursts worse.

troy

What lens material do you recommend?

polcat34
04-21-2014, 01:46 PM
I'm not sure if this would help, but I also have that issue.
I was at my doctors and say a ad in the waiting room for corrective lens that you wear at night and take out during the day. They temporarily change the shape of your cornea.
I will ask my doctor the next time I see him.
I hadn't connected the two until this post.
Thanks for posting, I am sure there are a lot of us out there.

solarguy
04-21-2014, 04:09 PM
What lens material do you recommend?

Optically, the best material is glass. But it's easily twice as heavy, and it's brittle--the last thing you'd want to wear around something that could potentially blow up.

CR-39 plastic is (optically) pretty close to glass, and the best of the polymer lenses. But for "bad" prescriptions, can get pretty thick, pretty fast. It is available in "safety glass weight", at least at some vendors. They make the lenses extra thick to give the shatter/impact resistance.

The vast majority of safety glasses use polycarb, because of its unparalleled shatter resistance. But optically, it is the worst of the 3 or 4 commonly available polymers.

troy

MI-1911
04-21-2014, 07:18 PM
Interesting! Thanks for the info Troy.

Bozo
04-22-2014, 03:59 AM
I know Cabelas in Grandville has a lot of scopes setup to try, maybe that can help a little until the eyes are corrected. My wife has the same problem, she's not in a hurry to find a red dot so she uses open sights.

balrog006
04-22-2014, 11:52 AM
This also gets better or worse depending on the optical quality of the sight... I have issues with the cheaper Bushnell TRS25 on the AR22 I built for my wife, but with the Aimpoint Micro T1 on my M4 it's much better, almost unnoticeable.

fr3db3ar
04-22-2014, 03:43 PM
Doc, I'm with you but I don't have an answer. I have astigmatism and I have an Eotech. I have the same issue until I turn the brightness wayyyyyyy down. I've leaned where in the blur the real POA is.

MI-1911
04-22-2014, 03:58 PM
I have astigmatism and I have an Eotech. I have the same issue until I turn the brightness wayyyyyyy down.

I have the same problem. EOTechs (projected lasers), are much worse than single dot LEDs, such as Aimpoint, and others.

Rara
04-25-2014, 08:16 PM
I am severely nearsighted and have pretty severe astigmatism in both eyes. Eotechs are all but useless for me, they flare into a huge blob of red. Aimpoints work well but still flare some. I run a 2moa T-1 and it is vaguely potato shaped for me, but still pretty small. I also had an Aimpoint PRO that worked the same as well. Keeping any sight on a dimmer setting always helps though.

Ironically, one of the best sights for a clean dot was a primary arms M3 clone.
I've thought about a triangle dot RMR, because they tend to stay clean for me, but I've been told they wash out badly under certain light conditions.

solarguy
04-26-2014, 06:58 AM
As annoying as it is, for non-critical work, the center of the fuzzy blob will get you on target pretty well. It's like focusing on your front sight post on the middle of the fuzzy bull's eye.

If there's any distance involved, or it's competitive/precision, the flare/astigmatism problem pretty much makes these sights a non-starter for those with significant and/or poorly corrected astigmatism.

troy

who dat
04-26-2014, 07:54 AM
solarguy, where is your office and are you taking new patients?

solarguy
04-26-2014, 09:38 AM
I'm not pimping for business or anything.

And I'm too far away for most of you.

I live in southwest michigan, pretty close to the line, and actually practice in Mishawaka Indiana.

If you're still interested, pm me and I'll give you the specifics. Yes, I'm accepting new patients.

troy

Sgt 45
04-26-2014, 12:47 PM
Interesting. I do have this problem and I notice on my Trijicon RMR that I have a nice 6 point star surrounding a very clear red dot. I just use the red dot and let it go at that.

fr3db3ar
04-26-2014, 07:13 PM
Correct me if I'm wrong but I think it doesn't help that most glasses make the best correction in the center of the lens, (I know to get my clearest vision I have to point my nose at what I want to see clear). When shooting I'm looking closer to the nose than center so the astigmatism isn't corrected completely.

solarguy
04-26-2014, 07:40 PM
Yes, that is the "optical center" problem.

troy

Oreo57
04-27-2014, 01:28 PM
Lots of good info here. Question for the professional: any reason to think shaded lenses might help? No astigmatism, but I have issues with night blindness/headlights, and found by accident that gray high index lenses helped.

Also, even people without astigmatisms see a "collection of dots" or a comma when they focus on the reticle in a cheap red dot; it's because that's exactly what they are =) :scatter:

solarguy
04-27-2014, 06:40 PM
On a red dot sight, sunglasses will only make it worse. The smaller your pupils, the more you get the "pinhole effect". This effectively hides some of the astigmatism. A shaded lens will make your pupils open up further and increase the halos.

For driving at night, which has been studied a lot, no shaded lens of any flavor has ever been demonstrated to make you safer or see better. And yet, lots of folks like a light amber tint which improves contrast. Wearing tint at night may be illegal in some states...


troy

agksimon
05-17-2014, 07:11 AM
As I posted in another thread:
My optometrist made me glasses that are slightly taller, top to bottom than I used to wear. He moved the start of the progressive lens power, up by a couple of millimeters and with a taller lens, there's more progression ground into them. You get used to them quite quickly and I can now, even at 69-years-old, see the front and rear fiber optic sights on my pistols with no problem. If it's dimmer light and using regular sights, I can very slightly slide the glasses upward for more power and it works very well.
It also seems to help when using my red dot on my pistol. I don't get the commas anymore, but still get some starburst, depending on how bright I make it.

CAPTP
06-09-2014, 10:37 AM
Could just be the shooter! ;)