Within the context of the question that was put and the comments leading up to it the answer is yes. If you choose to answer one part of question out of the context of the original discussion then the outcome may be different. The real matter was do they set both eyes the same focal length and the answer is yes.
Weasel. That was not the question that was asked
"Do they set both eyes to a fixed infinity?"
The answer is of course no.
No one is stupid enoght to believe the question was 'do they set the eyes the same?' Of course they do. Why would they not?
Not necessarily "of course". I would expect the lens to be set to a distance that gives good vision at some useful distance without needing to wear glasses. And the two choices are probably infinity so you only need to wear glasses for reading and other close work (maybe needing a selection of different glasses for different distances) or else reading, so you only need to wear glasses for longer distance such as driving and walking around outside.
Because if they set one eye to infinity and the other to reading distance then *if the brain can cope with it* you have good vision at both ends of the distance range without needing glasses for either. My question was "is that feasible or can the brain not cope with ignoring whichever image is out of focus?". I'm guessing that it isn't, otherwise people who haven't had a cataract replaced would wear glasses that had lenses of different strength so a single pair of glasses, worn all the time, will cater for all situations without the need for multiple pairs, bi/tri-focals or vari-focals. (*)
What is the normal distance that cataract lenses are set to - ie the one that most people choose if they have a choice? Infinity?
I'm surprised at the range of distances that my mum's cataract lenses can cope with: she only needs glasses for reading, and can see acceptably well from about 10 feet to infinity. Are modern cataract lenses capable of adjusting slightly using the same muscles that previously adjusted the eye's own lens, or are they still a fixed focal length?
(*) As an aside, why do some people cope better with vari-focals than others? When I first needed reading glasses, having previously only needed very weak distance glasses, I was offered vari-focals. The optician offered me a deal which gave the same price for either one pair of vari-focals or two separate single-vision glasses. After the sight test and the measurements of the exact locations of my pupils (because vari-focals depend critically on looking through the exact centre of the lens) I was given the vari-focals. And the effect was *horrendous*, even after wearing them for several days to give my eyes/brain chance to get used to them. There was an objectionable amount of parallelogram distortion: if two vertical lines moved across my field of view, they went from \\ to || to //. Likewise, if I moved my head slightly while looking at the same object, which requires the eyes to swivel to keep the object fixed, I got the parallelogram distortion. The optician did another sight test and re-checked the eye separation measurements, and all was in agreement with the previous tests. So they offered me the fall-back solution of separate distance and reading glasses at no extra cost.
Utter total bollocks
When age started making it more difficult to read (and use a computer) I ordered up some contact lenses that were sort of half way. And although they did make reading OK, I really couldn't put up with the poorer distance vision. Seemed most unnatural to me, since I've had corrected vision from a pretty early age. So soon just accepted I'd have to use a reading aid. Might be difference for a presenter on TV etc, though. ;-)
Since my contact lenses correct for distance, ready made reading etc specs are OK. And so cheap I can have enough to leave them were needed. ;-)
Some do apparently get on with one normal eye one short sighted. But I really can't see that being as good as having as near perfect distance vision as possible.
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