Posted , 9 users are following.
See the first image -- a defocus curve. So the ZFR EDOF lens matches the LogMAR of a regular monofocal at its best focus? Does anybody believe that this is actual research?
If the term LogMAR was not there, then I could see some other interpretation. But it is there.
Does anybody have an interpretation that is less cynical than mine?
0 likes, 34 replies
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jimluck trilemma
Edited
I grabbed another defocus comparison at random off the internet. This is Symfony (a diffractive EDoF lens) vs a monofocal. Same thing -- the 2 IOLs found to be equal at peak acuity on static; Symfony slightly better than monofocal at peak acuity on dynamic. Article is "Comparison of dynamic defocus curve on cataract patients implanting extended depth of focus and monofocal intraocular lens"
trilemma jimluck
Edited
How would you account for that?
Do you accept the claim (figures don't lie)?
Or is there some hocus pocus focus (liars figure)?
RonAKA trilemma
Edited
I don't believe it either, but there are a number of claims that J&J makes that I don't believe. It seems that they never lose any contrast sensitivity with these non monofocal lenses, and that does not make any sense. Possibly it is in the way they test.
jo61855 trilemma
Posted
VectorVision:
"Contrast sensitivity measures two variables, size and contrast, while acuity measures only size."
"Contrast sensitivity is a person’s ability to see low contrast images in the real-world, such as a street sign on a dark roadway, a flower pot sitting on the floor of a dimly lit garage or the size of the step height for a sidewalk at night. Contrast sensitivity is unlike the visual acuity test, “Big E Chart,” which measures only how well a person can identify high contrast black-on- white letters. Using low contrast images, contrast sensitivity testing can detect subtle changes in vision that are hidden by visual acuity."
I read a report that Blue Light Blocking IOLs improve CS vision. The thesis is that eyes of people as they age lose ability to shield vision from blue light which decreases their vision contrast sensitivity.
RonAKA jo61855
Posted
I think blue light filtering increases as one ages. Essentially the natural lens gets more yellow which increases blue light filtering, and this increases even more when cataracts develop. IOLs increase contrast sensitivity with blue light filtering by blocking chromatic aberration.
trilemma jo61855
Edited
So this contrast sensitivity factor, how might that affect a LogMAR defocus curve? You don't propose that the EDoF lens would be helped by this, would you? So my obvious point is how do these charts show the LoGMAR at the best focus to be as good as the LogMAR with a monofocal lens?
And while we could say that LogMAR does not measure all aspects, note that the defoxus curve charts I complain about actually say "LogMAR" on the vertical axis. That would see to be specific.
I have no opinion on whether a blue-blocking feature is net good for an IOL. If you try this search, you will find discussion, largely from people selling sunglasses or shooting glasses:
"blue blocker" glasses
One thing, tho.. You will read that blocking blue light is beneficial before bed, because it blocks melatonin production. From that aspect, it would seem to be better to use light sources that have a lot less blue light, but do I want blue to be filtered at all times? I still don't have an opinion on that.
RonAKA trilemma
Posted
Blue light blocking eyeglasses are mostly a scam for those who do not have IOLs. Blue light blocking in IOLs is worthwhile as it is only restoring the blue light blocking that a young person's natural lens has. It also reduces the chromatic aberration that higher index of refraction IOLs have.
jo61855 trilemma
Posted
The authors of the paper you cited would have to answer your question about CS. If interested you can try to contact them. Acuity (LogMAR) is but one part of an IOL decision.
trilemma jo61855
Posted
If there is not a measurement that describes the quality, then I don't see incorporating it in my decision.
My thesis in this thread is that the people who show their EDoF lens with the same peak LogMAR as a monofocal lense are not the honest technical people. They are the deceptive marketers.
When they label a graph with a LogMAR vertical scale, they should be talking about LogMAR, and not some unspecified qualitative aspect. If they want to talk about some other aspect, then they should say so.
Yes, there are other factors in an IOL decision. Convenience, price, likelihood of a bad outcome, and more. But you would agree that LogMAR at various levels of defocus is also important. To be useful, the defocus curves would need to be accurate and honest. Am I being unfair?
Guest trilemma
Posted
Not sure why this is so complicated. Logmar = accuity. You can have two images that are equally sharp but one is vibrant and colourful and the other is dull and washed out… and the logmar is the same.