I am skeptical of this "research" -- a defocus curve

I understand this to mean LogMAR doesn't measure "optical quality"

I don't agree with that. It says ""In summary, the ZFR00 exhibited a continuous range of vision and a smooth defocus curve, while the ZCB00 provided superior objective optical quality""

So it says the monofocal had superior optical quality, but the EDOF lens did better farther away from the focal point. In other words, the EDOF had a better LogMAR away from the peak performance distance, but did not do as well at the peak (distance vision). This makes sense, and I believe it. What does not make sense are the curves that show the same peak LogMAR at focus for regular IOL and for EDOF. I suspect those graphs are not limiting themselves to truth and fact.

OK. Now I recognize that study, and distrust it.

I trust this statement ""In summary, the ZFR00 exhibited a continuous range of vision and a smooth defocus curve, while the ZCB00 provided superior objective optical quality""

That seems incompatible with figure 2a, but compatible with figure 2b

So why is the story so different between figures 2a and 2 b? I have a follow-up post with links, that I anticipate will be approved.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9890684/ is the study.

https://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/tileshop_pmc_inline.html?title=Click%20on%20image%20to%20zoom&p=PMC3&id=9890684_40662_2022_323_Fig2_HTML.jpg is the graph.

I find figure 2a implausible, and figure 2b to be plausible. What is the difference? First, they decided to invert the LogMAR scales, which is not in itself a problem. But to be consistent would have been better IMO.

But my real complaint is that despite the same labels, they seem to be inconsistant with each other. My suspicion is that in 2a, they normalized the static numbers (whatever that means) to zero. But they did not change the labels to indicate that. Did I miss something there, or is 2a not compatible with truth?

Your: "I understand this to mean LogMAR doesn't measure "optical quality.""

From Wikipedia:

"Zero LogMAR indicates standard vision, positive values indicates poor vision, and negative values indicates good vision. This is less intuitive than other VA notations. However, LogMAR is actually a notation of vision loss."

If I assume that any lens that made it to market will get a healthy patient to 0.0 LogMAR at its peak acuity with optimal lighting, would I then not expect that a monofocal lens would give better than 0.0 (in other words negative) LogMAR?

After moderation, I will have a follow-up posting appear with a link to "Comparison of dynamic defocus curve on cataract patients implanting extended depth of focus and monofocal intraocular lens". Figure 2a I find implausible. Figure 2b of that same paper, is plausible to me. They tell conflicting stories IMO.

Is this the link you wanted?

https://pubmed.ncbi.nlm.nih.gov/36721199/#:~:text=Conclusions%3A%20The%20EDOF%20IOL%20provided,visual%20performance%20post%2Dcataract%20surgery.

Logmar = accuity (how in-focus an object is for a given distance) not quality. It's a different way to say the same thing as Snellen (i.e. 20/20). There is also a decimal scale. There is no such thing as "better than 0". And yes the chart (Tecnis 1 vs. Synergy) is accurate because it is only measuring how in-focus an eye chart is at different distances. That's all. Synergy has a wider range of focus (you can see in-focus closer up) but focus is only one variable. Image quality and contrast will suffer across the entire range of vision with Synergy because the way it is achieving the wider focus range is by spreading out the incoming light. So there is much less light at every focus point than the Tenics 1 at it's optimal focus point. The best image quality by far is a monofocal but it only has one optimal focus point. So you need reading glasses for up close. This means that reading image quality with a Tecnis 1 WITH reading glasses will blow away reading image quality of a Synergy without reading glasses.

No. You seem to leap from the correct assumption that there is no free lunch in optics to the incorrect assumption that the price of lunch has to be a penalty in peak acuity under optimal lighting. I will rephrase what I said "Probably no lens is going to make it to market if it won't match the peak acuity of a monofocal under optimal lighting." The penalty for EDoF or multifocality will be paid in other aspects of visual performance.

There is no such thing as "better than 0"

There is. Look at the "LogMAR chart" entry on Wikipedia, and see the "Visual acuity scales" table on the right maybe 50% down the page.

I agree with most of your sentences. Thanks for giving it some attention and analysis.

LogMAR measures how small of an angle you can resolve, but that determines your ability to read charts. If the lighting is bad, your LogMAR would be worse. So I expect they standardize the brightness for eye tests.

The term LogMAR is an acronym for the Logarithm of the Minimum Angle of Resolution.

Synergy has a wider range of focus (you can see in-focus closer up) but focus is only one variable. Image quality and contrast will suffer across the entire range of vision with Synergy because the way it is achieving the wider focus range is by spreading out the incoming light. So there is much less light at every focus point than the Tenics 1 at it's optimal focus point. The best image quality by far is a monofocal but it only has one optimal focus point.

So wouldn't the monofocal have a better LogMAR at the optimum distance/focus?

So wouldn't the monofocal have a better LogMAR at the optimum distance/focus?

No. Again LogMAR doesn't mean image quality. It just means how in focus something is at a given distance. 0 LogMAR or 20/20 or 1.0 decimal or 6/6 are all the same thing.

.

A monofocal has better overall image quality at it's optimum focus distance but not better accuity. A person with a Synergy can read the 20/20 line just as easily as someone with a Tecnis 1. Again, eye charts only measure one single variable… accuity. I can still do 20/40 on a chart with my remaining cataract eye which objectively sounds ok but subjectively the image QUALITY of that eye is crap.

You have done a good job of pointing out what we disagree on.

No. Again LogMAR doesn't mean image quality. It just means how in focus something is at a given distance. 0 LogMAR or 20/20 or 1.0 decimal or 6/6 are all the same thing.

There is an easy disagreement. Somebody with a significant cataract, but the lens is in focus, will not achieve 0 LogMAR. So IMO, LogMAR pretty much means image quality.

In the defocus curves, that is what the LogMAR scale means-- what is the image acuity (quality) at x amount of defocus.

Not necessarily. Take two people for instance:

Person A, 50 yo with a significant cataract. No other issues. Uncorrected vision 20/100

Person B, 20 yo with myopic eyes yet clear youthful natural lens. No other issues. Uncorrected vision 20/100.

Both persons A and B can achieve 20/20 vision acuity (LogMAR 0) with spectacles.

However, the image quality reflected into each person's retina is different. The image perceived by person B is of a higher quality than the one perceived by person A simply because the latter's cataract is an "interference": colours are more faded, there is a bit of a yellowish hue, there is haze/glow around lights at night, diminished contrast, etc.

Both person A and B will report a corrected vision of 20/20 (acuity), which is true and we can measure that. But person A will never know how much brighter and more vibrant the colours appear (quality) to person B. That wonderful secret will go with B to the grave 😃

So for me, acuity is a prerequisite for quality, but in and by itself is not quality.

Take two people for instance:

Person A, 50 yo with a significant cataract. No other issues. Uncorrected vision 20/100

Person B, 20 yo with myopic eyes yet clear youthful natural lens. No other issues. Uncorrected vision 20/100.

Both persons A and B can achieve 20/20 vision acuity (LogMAR 0) with spectacles.

I don't agree. The young myope can expect to be corrected to LogMAR 0.0 (20/20) or better. The person with the bad cataract will have a hard time being corrected to LogMAR 0.3 (20/40). In fact, that can be the border between Medicare paying for/toward IOLs or not-- can the person be corrected to 20/40 or better?

In support of my thought that Medicare would only pay/contribute toward an IOL for a cateract if the eye has deteriorated to not being correctable to 20/40, I have some references. But yes, there are some other criteria that can get around that.

https://www.mmplusinc.com/kb-articles/medicare-requirements-for-cataract-surgery

The patient has a best corrected visual acuity of 20/50 or worse at distant or near; or additional testing shows one of the following:

Now the glare testing or one of the other things can let Medicare pay for the IOL surgery. I expect you might say that the glare testing will let our person with a cateract get an IOL even tho that person is correctable to 20/20. In that case, we are back to your thought that somebody can be corrected to 20/20 while having a significant cataract. So we would continue to disagree as to whether that can happen.

https://www.bcbsm.com/amslibs/content/dam/public/mpr/mprsearch/pdf/2026333.pdf -- Michigan Blue Cross uses the criterion of worse than 20/40 with some other factors.

The patient has a best corrected visual acuity of 20/50 or worse at distant or near; or additional testing shows one of the following:

Thanks for clarifying.

I think we're talking past each other 😃

so the word Acuity simply refers to looking at the eye chart?

I think we're talking past each other 😃

https://en.wikipedia.org/wiki/Talking_past_each_other

I viewed it differently.

since the definition of acuity is "to see accurately and clearly" (which in my world means quality) how does the statement { Logmar = accuity (how in-focus an object is for a given distance) not quality } not mean quality?

seems like these words are a bit fuzzy

I followed your link on Medicare. I says if you have a cataract and you say it is impairing your ability to function and the biometry has been done and the risks have been explained, and other causes have been ruled out, and surgery is likely to help you are covered. The stuff about 20/50 is on an "or" branch of the decision tree that you can don't have to go down. You can skip it because it says 20/50 OR the patient says it is impairing their ability to function.

Quality isn't a scientific metric that can be measured as a single variable.

Because quality is the result of multiple factors not just image sharpness,

quality is a completely subjective experience anyway