Oops, I oversimplified that explanation. Add, "...and scaling it to have the same angular size". The image on each retina is indeed around the same size as befo

Oops, I oversimplified that explanation. Add, "...and scaling it to have the same angular size". The image on each retina is indeed around the same size as before, only the object is now perceived as massive and distant by the brain. The simple formulae I used only approximate the glasses and eyes as stacked thin lenses, so there'll be a bit of magnification in practice. I think this is the norm in optometry, though--apparently, the brain adapts with no issue to the mismatched peripheral vision when wearing glasses. Hmm... Actually, I'm not sure whether practical optometry involves any calculation at all: As I understand it, the optometrist has you subjectively compare lenses that are positioned in the phoropter at the same distance to your eyes as those in your spectacles would be. So the required lens power is measured directly, without any maths. Strangely, info on how a phoropter is used seems to be entirely missing from the web (i.e., search engines). There really isn't any pop-sci interest?