TargetTalk

Hi all, I'm hoping for a little advice regarding my eyesight, normally I would go to the optician but with the current situation that's impossible. A bit about me, I'm UK based 60 years old, I used to shoot smallbore prone 25 and 50M in my younger days with some success but gave up for a number of years. a few years ago I bought am Anschutz 8002S2 just to play around with on my own in my garden uncompetitively but again due to a family illness it didn't really see the light of day until recently. I do wear glasses for both long and short distance normally, both pairs are varifocal so they don't lend themselves to even trying to shoot with.

My problem, I think it is caused by astigmatism, I get a fuzzy blob just below and to the left of the centre of my line of sight, it moves around a little and is worse sometimes than others, it looks a little like a floater but it isn't it only appears when I look through any very small aperture. I have a Gehmann 544MC iris/correction lens on the rear sight which does me fine for focus and the iris if I open it up reduces the blob a little but in return makes it harder to centre the foresight. Another problem I have is a wondering focus in my right dominant eye which I could live with if the fuzzy blob wasn't there as it seems to distort the target badly and makes even guessing the aim almost impossible, that happens maybe 30% of shots, I have a number of ways of overcoming it like shutting my left eye, trying to strain to get focus, resting and breathing which can work but none of them are ideal. On the odd occasion the fuzzy blob is lower and I have a clear view the target whether in focus or not will always be concentric so it's OK like that. they look a little like these pictures but vary quite a lot but don't really show how bad the picture is when it is bad, think slow wobbling jelly





I take it I need to get myself a lens, either attached to the sight or spectacles to fix this? Any other advice you could offer would be a great help but it is only me in my garden, nothing competitive so rules don't really kill any solution

Thanks

Colin,

Correcting as astigmatism isn't that difficult. When the lock down restrictions ease go to an optician. Ask for a lens with your distance prescription +0.5*, including the cylindrical correction for astigmatism. Ask them to mark the lens at 12o'clock so you can orientate it. It doesn't matter whether you put the lens in special shooting frames, or a lens holder on the rearsight, both place the centre of the lens square to your line of sight. If you only shoot one rifle, the lens holder is simpler and cheaper. Some opticians struggle with these small lenses, but ask around and you'll find one who can. I paid about £30 last year.

EDIT - However your diagrams don't really show astigmatism. This really just distorts the target and foresight into a rugby ball shape not a circle. A fuzzy bpib that obscures the target sounds more like a cataract, or defect in the eye. I'm not aware that you can fix a cataract with a lens.

*The extra 0.5 on the lens gives distance focus for aperture sights without using the Gehmann dioptre. NSRA (British domestic) competition rules allow spectacle lenses and a Gehmann-type dioptre (8.4.1.2), but if you are correcting for astigmatism, you might as well put it all in one lens. The extra +0.5 should make your sight picture less sensitive to aperture size, as you aren't reliant on the aperture for focus. A larger aperture won't concentrate the light onto such a small area of the retina.

Thanks Tim, it's not a cataract as far as I'm aware, I went to the optician a few weeks before we locked down, I have a history of glaucoma in the family so the optician really gave my eyes a good going over. There was no problem other than the drifting focus which he said was common in under 6 year olds. I wonder what that blob is then? I will speak to him as soon as this is over. It's not the end of the world but it does make a few shots more of a chance than a probability which is a shame because otherwise it's all going very well

Question: Does your floater move with the movement of the eye? In other words, when you look straight at the target, then without moving your head quickly look to one side and back, does the floater 'finds its way back and re-position' itself in the same spot? If so, Google Asteroid hyalosis.

Usually, floaters drift slowly downwards by themselves.

Disclaimer, I am in no way an eye expert, just a shooter that has to deal with Asteroid hyalosis.
Cheers,

No, it's static, same sort of shape always and in the same place give or take, strangely enough I tried the other eye earlier and I had the same thing but a mirror image, I also tried with my glasses in the hope that if it went it might be astigmatism but it was still there. I don't think it's a floater, there is no hint of it at any other time. If I reduce the size of the iris it gets darker and more opaque and if I open it out to the full 3mm it all but disappears but that is useless for aiming. It isn't dust in the sight either, I get the same thing looking through any small hole

No way to know unless you see an optician. It could be an astigmatism, but you never know unless you consult with a doctor. It's best to wait it out and see an optician first and I'll tell you why. I had a similar issue. The rear peep hole appeared oval shaped along an 8 o'clock to 2 o'clock axis and a ghost image of the inside of the peep hole which was very detailed. It was very difficult to center the front ring on my target. Your blob could be a similar ghost image, just not detailed like my issue. Anyway, it was a very annoying issue and I spent all kinds of money trying to fix it myself including buying the Gehmann Vari-Focal Astigmatic Iris. Nothing worked. I went to my optician to ask if they could make a custom lens as an experiment to see if that would help. They measured my vertex distance to the rifle sight and then ground a lens with my prescription and astigmatism correction for about $100 (might be cheaper for others since I have a high and complex prescription). My sight picture now looks textbook perfect and my scores went up. I should've went to the optician to begin with, it would've saved me money and frustration.

Thanks, that sounds encouraging, it sounds like the lockdown will be easing over the next few weeks, I’m definitely going to see the man and get his advice once things cool down a little. I had thought about the astigmatism corrector but it looks like it fits after the iris which seems like it misses the point but then the least glass between my eye and the target the better.
Out of curiosity at what distance is the focus point of your lens? With the Gehmann I’m finding the best results just past the foresight ring

I'm not sure what the exact focus distance number is, but I would say it's past the foresight. I have a 19 inch barreled airgun, a 24 inch Anschutz, and a 26 inch barreled Anschutz I'm able to use the lens on.

Thank you, I suppose for my purposes getting rid of the blob is the main thing, if I stick with the Gehmann 544MC then I could adjust the exact focal length to suit if need be although I would prefer not to. I have read in the forum that the lens should be far distance +1.5 diopters, I guess my optician could work that out for me. If I take the standard Anschutz disc and the Gehmann we could work something out

Colin,

You want distance +0.5 dioptres. If my maths serves me the larger the correction, the shorter the focal distance; adding +1.5 would bring the focus between the rearsight and foresight, rather than placing it ahead of the foresight.

I go from +1.25 to +1.75. A short sighted prescription gets smaller, say from - 2.0 to - 1.5.

Thanks Tim, yes 0.5 is what I read, my brain wasn't watching what my hands were typing!

Mine turned out to be an astigmatism in my left eye, cataracts in both and a convergence issue do to aged mussels. I would get what looked like a start rather than a dot looking through a red dot. Post cataract surgery, 20/20 in both eyes as long as one eye was closed otherwise I say double in bright light. So I now have glasses and shooting glasses with Prism adjustment and astigmatism correction in the left eye only. Doesn't both me since I still need reading glasses so these are progressive lenses and allow my to do everything.

Sure made a difference. BTW the cataracts were very minor and I didn't even qualify for my insurance to pay until I told them it caused me problems driving at night (which was suggested by the doctor) and the insurance approved them early.

Bob