In this discussion I'm speaking of the dynamic range of focus - the range of nearest to farthest objects your viewing system (eyes plus appliances) can bring into focus.
AKA "accommodation" which is not the same as depth of focus, and you have to some degree interchanged those terms in one or more of your previous posts.
You can think of that range in two ways. First, you can simply think of the "nearest" and "farthest" possible focus distances. Alternatively, you can think of (farthest minus nearest) as the dynamic range, and the median of those two distances as the "center" of the focus range.
You could but what's the point?
As our lenses harden at 40YO+, one effect is that center moves more distant. This is why most people start requiring "readers" for near vision. For those of us with myopia, our required correction actually reduces. I used to be nearly -5.00 diopters and lately I'm in the low -4.00's. Gets lower every couple of years.
No clue what you mean about "the center moving more distant". Distant to WHAT? And yes, the tendency is to get less myopic or more hyperopic as we age due to increased density of the crystalline lens from buildup of metabolic byproducts over a person's lifetime, which also contribute to its decreased flexibility.
I think you're complicating the issue with all that stuff about the center moving this way or that way. Point is the lens becomes less flexible as it becomes more rigid due to the buildup of metabolic byproducts, it can no longer become more convex and focus parallel (distant) or divergent (near) light rays to a point.
The lens hardening also makes it more difficult for your eye muscles to reshape the lens, resulting in an overall narrowing of that dynamic range. Said differently, the "nearest" and "farthest" get closer together. This is why most people end up with bi/trifocals or progressives.
Again, that whole "nearest and farthest getting closer together" bit is a confusing bit of jargon that means nothing to me. As the lens ages, it's more rigid, it cannot become more convex through focusing of the ciliary muscles pulling on the lens zonules and so near objects become out of focus, so to clearly view these objects we need convex lenses either in the form of eyeglasses, contacts, or corneal reshaping, or replacement lenses, the exception being myopes who can see near objects fairly well without any correction or who may need a concave lens correction to decrease the myopic effect of their eyeballs.
Think of them as a transmission for your lenses... they normalize the narrowing (focus or RPM) range of one system (eyes or engine) to the wider range required by the outside world (vision or wheels). Bi/tri's are like a manual transmission, with discrete ratios. Progressives are like a CVT!
No offense but I prefer not to think of it that way, it's way too confusing and not really all that relevant.
It is this second part that means I'll never be without corrective lenses of some type. My prescription is "getting more normal" but I'm losing range, just like everyone else does at 40YO+.
If you get cataract surgery with accommodative, multifocal or bifocal IOLs you may not require additional refractive correction. Based on your stated Rx, you will never get to plano (zero correction) for distance due to natural aging. My best guesstimate is you'll level off at about a -2.50 which is perfect for viewing 16" objects.
