Sharpnesss of Lense vs Eye Capability

Getting the best value for your money when it comes to eyeglasses, sunglasses, eye exams, and contact lenses.

Postby JerryM » Mon Sep 05, 2016 8:08 pm

I recognize that modern technology has resulted in better lens. However it is one thing to claim superiority based on laboratory tests and yet another when considering the capability of the human eye. Has technology advanced past the ability of the eye to take advantage of the superiority of the lens?

Has there ever been a test that determined that a $400 set of lens results in appreciably better vision of the individual? Obviously it would require a fairly large number of people to do the test, and the test should be one where the people being tested do not know which lens they are using. :?:
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Postby george » Mon Sep 05, 2016 9:53 pm

Interesting question. When talking about the ability of the human eye to differentiate lens differences, there are a few factors involved. Starting with single vision lenses, my understanding is that most people can differentiate about a 0.25 diopter difference, which is the difference between the various lenses the eye doctor uses in their machine to check your vision (phoropter). I've read that some people can tell the difference at a 0.125 diopter level, but I find that usually the eye doctor can get down to two lense choices that look almost identical to me. I can't imagine trying to determine which is better at a 0.125 diopter difference.

Additionally, the glasses themselves are allowed some variance in production. I've read the allowed amount is 0.25 diopters, but I would guess that most eyeglasses are made more accurately than that.

So - based on the above discussion, it seems that the technology of single vision lenses is already able to surpass what the human eye can discern in most cases. Single vision lenses are generally not too horribly expensive, but you would pay more for high index (thinner) and polycarbonate (shatter resistance). The real increase in cost is when you get into progressive lenses. I remember reading some studies where manufacturers did compare the types of lenses, but it was an older publication. Essentially they did compare two of progressive lenses and they found one was preferred more often than the others. I'll see if I can dig up the study.

Bottom line (as best I can tell) - the lenses can be made even more accurate, yet the human eyes is not able to tell the difference.

One other aspect, though, is the high cost of progressive lenses, and whether that extra cost is worth it. I have yet to see a good study of progressive lenses, at least more than comparing two designs. This seems to be the most important question - are the expensive lenses worth the extra cost? Are the lenses actually better than the cheaper lenses?
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Postby JerryM » Wed Sep 07, 2016 1:22 pm

Thanks, George,
I have friends who are convinced that their $400 progressives are necessary for them to see. They take the advice of their optometrist, and never consider anything else. The wife was wanting some bifocals for reading and I suggested that Zenni would be good and inexpensive. I also thought they should try a pair of Zenni progressives, but they were convinced that only the recommendations of their Dr. would suffice.

I recall around 1963 when Leica brought out binoculars. They were about $400. I had a pair of $60 Bushnell binocs, and so three of us on a hunt sat on a mountain and compared our binocs. All of us agreed that my Bushnells were just as good as the Leicas as far as our vision would permit. Yet all the magazines praised the Leicas as superb and the best available. I do not doubt that on a bench the Leicas would have been far superior to my $60 Bushnells. I guess our eyes did not have an imagination. I am sure today we could easily find any good brand that would be better, but I am persuaded that much is hype. I also realize that construction is very important in optics.

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