
I have posted about this before, but to summarise.
I tried all my iron-sighted rifles and was able to determine that if I can put the front sight 900mm forward of my eye or more, then I can actually focus it. I think I only have two or three rifles that this applies to, the majority are far shorter than this. The carbines that I mainly shoot with have 18" to 20" barrels, and short butt stocks, not the 29" barrels of the milsurps. For now, I'm still shooting reasonably well, I'm not getting frustrated because I can't hit what I'm aiming at, it's more that it takes a great deal of concentration to guesstimate where the invisible front sight would be in the rear sight, and place that over my target. I think a lot of it is mainly relying on a consistent cheek weld behind the rear sight. I have actually tried two rifles (JW25A and M96) with the front sight missing entirely and still grouped hardly any worse. On the other hand I also tried the JW21 with the rear sight missing and was still dinging the steels fine with just the front sight, but that was before I started noticing eyesight issues.
I also used the RPR (due to its removable cheek piece) to shoot right-eye/right-handed, left-eye/right-handed, and left-eye/left-handed off the bench. My vision in my left eye is excellent, zero issues at all, but my left-handed trigger control is abysmal, particularly when trying to shoot precision off the bench. It's less of an issue just practicing offhand on steel. I have pulled triggers right-handed for several hundred thousand rounds across rifles, guns and pistols, but shooting left-handed equates to probably just a few thousand rounds (we did a fair bit of weak-side in IPSC pistol shooting so I practiced a lot). Learning to shoot better left-handed is something I'm going to have to do, but it's going to take time.
My optometrist found a cataract starting in my right eye a few months ago. To 99% of people it would barely be noticeable, to a shooter it's an issue very early on. I saw an eye surgeon today to find out a bit more about it, and more importantly, how we fix it. My eyesight is excellent other than this cataract. I do wear reading glasses for close stuff. We can do a fairly simple operation to remove the existing damaged lens and insert an artificial lens, not difficult at all, but it does have potential drawbacks. Nothing he does will make my right eye as good as my left eye already is, apparently they only make the lens in half-diopters so he can only pick one that will get us close, it's unlikely it'll be perfect and match the natural left lens. Odds are about 20% that after the operation I would need to wear glasses for normal and long distances, and for driving. So, overall, my eyesight may well become an issue in general life that it currently isn't, it's only an issue for shooting. At some point in the next few years we will have to replace the lens, that's unavoidable, but I would hope that with each passing year the odds of negative side effects also reduces. So waiting seems the sensible option for me just now.
But waiting also means I need to find ways that will allow me to improve my shooting, or at least make shooting easier

While this is primarily an iron-sight issue, I'm finding it difficult to precisely focus scope reticules also, not as bad as iron sights, but enough to affect my group sizes on targets.
The obvious direction is prescription shooting glasses or contact lenses, which I will investigate. There are some optometrists in Oz that come up in a Google search for shooting optometrists, so I'll chase up their advice.
I've also seen a lens system that you mount on the rifle behind the rear sight, not cheap but perhaps worth the experiment also. This doesn't appear to be very useful when I shoot a variety of rifles though.
I know I'm not the first shooter to experience this, and perhaps other shooters are also starting to wonder if they have problems.