Why the Rayone EMV is not popular in the US even though it might be better than the Eyhance

That was a good summary of those iols. I am surprised the makers don't mention that in their marketing.

Ron,

The lens that is pretty much my only choice for my right eye is the Zeiss AT Torbi Toric. I am pleased (I think) to see it is aberration-neutral. I have a lot of higher-order aberration in the right-eye cornea, which gives me good depth of field. I wouldn't want to lose that, even if it gained me some acuity. I believe an aberration-neutral lens will give me best depth of field for a monofocal. Do you agree? Do you have any comment on this lens?

Article that has defocus curves for Rayone EMV and Eyhance : https://rayner.com/wp-content/uploads/2021/11/A-Clinical-Comparison-of-RayOne-EMV-and-TECNIS-Eyhance.pdf

"A Clinical Comparison of

RayOne EMV and TECNIS Eyhance

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I am afraid I do not know much about this lens. I recall it is one of the few lenses that will have enough cylinder to correct your high astigmatism.

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It would seem that the astigmatism must be in the cornea, so I wonder if laser surgery prior to cataract surgery may be an option to reduce the astigmatism to bring it into the range of more standard lenses? But, there are issues with using laser as well...

laser surgery is a bad idea on a cornea with keratoconus my doctor says, because it is already structurally weak.

Yes, my right eye 8.25 cyl astigmatism is 100% corneal. Put a scleral contact on that eye and presto! no astigmatism. (And presto! all my natural EDOF goes away and I can't read the dashboard).

It would seem that the astigmatism must be in the cornea, so I wonder if laser surgery prior to cataract surgery may be an option to reduce the astigmatism to bring it into the range of more standard lenses? But, there are issues with using laser as well...

If someone were planning to have both IOL implant and laser, I would think that it would be better to have the IOL implant first. Then the laser to fine-tune.

I am not sure what that defocus curve really is. Rayner has played some games with defocus curves that are the result of using mini-monovision at -1.25 to -1.5 D. EMV stands for enhanced monovision. The article says bilateral emmetropia was targeted. Does that mean the two eyes combined after mini-monovision tested binocularly.

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If this curve really was what one lens could achieve, it would easily qualify as an EDOF lens like the Vivity. It is not advertised as such.

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I guess what I would like to see is a monocular defocus curve for these lenses. That would show the real story. Something seems fishy.

Yes, I have the keratoconus issue too, and the laser surgeon said the same thing. It is a shame as the astigmatism associated with keratoconus is irregular and custom Lasik could potentially correct it. The surgeon I went to says the cornea is thin and the results would be unpredictable and the keratoconus could get worse.

That was what I did. My cataract surgeon said that was possible. Then after cataract surgery I went to the laser surgeon and was then told it was not possible. If I had known that before the cataract surgery I would have gotten a toric lens.

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Lasik is good at correcting astigmatism, but at the same time it reduces myopia. It is very difficult to increase myopia with Lasik. So, it depend on where you end up.

Here is an article where the doctor presents the defocus curve for one patient using the Rayone EMV. Although the curve is binocular, there is a table of values above the graph for each eye individually so one could construct the monocular curves and the targeting is stated there also (0.5 diopter difference) https://crstodayeurope.com/articles/early-experience-with-the-rayone-emv-toric-iol/early-experience-with-the-rayone-emv-toric-iol-2/

Mine isn't thin. In fact, an inexperienced ophthalmologist-in-training said lasik would be no problem on it because thickness was normal.

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My experienced doctor said he could do PRK touch-up after cataract surgery on it if there was a refractive miss but would not risk Lasik and Lasik would not be necessary. The issue is the shape of it (big beer belly) is structurally weak.

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Mine isn't irregular in the central zone relevant for vision. Huge, but regular.

Asked about cross-linking to stabilize it more, he said at my age (73) natural UV would have cross linked it enough.

The surgeon I went to seemed concerned that my keratoconus was still progressing at my later age of 73. He said it was a condition which usually occurs in the teenage years. I have seen him a couple of times now and will see him again next month and I will have to ask him if there is any indication of progression.

If I was looking for a monofocal with an extended depth of focus I would take a close look at the asphericity status of the available lenses. Asphericity does add depth of focus at a small cost in visual acuity proportional to the amount of residual positive asphericity. Of the common lenses these are the positive asphericity value in order of least positive asphericity, and least depth of focus, to the highest positive asphericity and most depth of focus:"

Ron,

You seem to be using "asphericity" as a substitute for "spherical aberration" and that confuses me because I don't see any articles that do that. I don't see positive and negative "asphericity" being discussed. I see postive and negative spherical aberration being discussed. Could you please clarify?

I don't see writers saying "asphericity" adds depth of field. I see them saying it improves contrast sensitivity when combined with negative spherical aberration to cancel out the positive spherical aberration of the cornea, thereby reducing total spherical aberration of the system. And I see them saying the price of this increase in contrast is reduced depth of field. I also see them saying that there are aspheric lenses with zero spherical aberration in the IOL, which allow the positive corneal SA to give the total eye system (IOL + cornea) greater depth of field, at the cost of reduced contrast. see for example: https://journals.lww.com/jcrs/abstract/2009/03000/comparative_study_of_aspheric_intraocular_lenses.27.aspx#:~:text=The%20Tecnis%20Z9000%20IOL%20has%20a%20prolate%20anterior%20surface%20designed,277%20mm.

I don't see articles quantifying the degree of "asphericity" of different lenses. I do see them quantifying spherical aberration.

In the graph you posted from B&L (with the red dot you added), the vertical axis is the degree of spherical aberration (SA), not "asphericity". And it's not the SA of the lens but that of the entire optical system in an average eye with the lens. The lens B&L is touting is aberration-free, while non-aberration-free lenses tend to cancel out the patient's natural SA, thereby reducing depth of field. The aberration-free IOL allows the entire optical system to have MORE SA and therefore more depth of field. ( Less aberration in the lens => more aberration in the total system including the lens => more depth of field)

Spherical aberration is not the only way to get depth of field. The Eyhance gets its increased depth of field by gradually changing in power from the periphery to the central zone, not from SA. So I'm not sure why you put your red dot where you did on a graph of SA of the total optical system vs depth of field.

" “Eyhance’s periphery is the same as the Tecnis one-piece IOL, and this feature enables both IOLs to reduce spherical aberration to near zero. The two lenses have the same base geometry, and the difference in shape is in the range of microns, which still means a lot for the lens power. Because the power change is continuous, it’s not visible to the naked eye on the lens—i.e., Eyhance doesn’t have any rings or disruptive changes in power. In terms of optical design, both lenses are refractive and reduce spherical aberration to near zero.” Quote is from a 2021 Review of Opthalmology "Necomers" article comparing Vivity, Eyhance and Rayone EMV.

One of Eyhance's superiority claims is 30% better contrast sensitivity than the Tecnis monofocal, and I'm guessing it near zero SA is how they get that, and part of that guess is my inferring that the writer is referring to the SA of the total optical system including the IOL and the cornea. SA (of the total optical system) buys you depth of field at the cost of contrast sensitivity.

The Rayone EMV gets its extension of depth of field from SA. "RayOne EMV is designed with an aspheric anterior surface and unique inner optic zone which induces controlled positive spherical aberration to extend depth of field " (quote from Rayone literature).

Both the Rayone EMV and the Eyhance are aspheric lenses. Numerous articles refer to their "aspheric surface".

Asphericity and spherical aberration are different concepts. They interact, but they are not the same thing.

Spherical aberration of the IOL and spherical aberration of the total optical system of the eye including the IOL are also different concepts. Paradoxically, SA- free IOLs allow more spherical aberration of the total eye optical system in most eyes than IOLs that have SA. Often the SA of the IOL is introduced to cancel out the SA of the cornea, reducing the SA of the total system, resulting in better contrast sensitivity but less depth of field.

That's my understanding, anyway. I welcome corrections. We're all seekers here.

This article shows very different defocus curves for the RayOne EMV and Eyhance. They indicate the EMV is very slightly better for focus extension than the Tecnis 1, and not even close to the Eyhance.

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Laboratory Investigation of Preclinical Visual-Quality Metrics and Halo-Size in Enhanced Monofocal Intraocular Lenses Grzegorz Łabuz . Hyeck-Soo Son . Tadas Naujokaitis . Timur M. Yildirim . Ramin Khoramnia . Gerd U. Auffarth

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That passes the sniff test better than a lot of defocus curves.

The way I understand it is that lenses can be spherical, which I believe is a constant curvature and no power change from middle to outside. Or they can be aspherical and have a change in the lens. Different manufacturers use a different amount of negative aspherical power change from the middle to the outside of the lens. The amount they use combined with the average positive spherical aberration of 0.27 um of the cornea results in a net spherical aberration. Aspherical I believe just means not spherical but there can be different amounts of it. Some manufacturers are quite transparent about the amount they use, and some are not. Eyhance for example does not disclose the amount of the spherical aberration in their aspheric lens. They say they vary the power of the lens with the radius of the lens (which is asphericity), but do not quantify it. When I put that red dot on the graph this was not based on a published number. I simply took their claim as to how much depth of focus the Eyhance was said to have over the Tecnis 1 which is on the graph. So, I just put the dot on the curve based on this extra amount.

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So I think the short story is that aspheric lenses are simply non spherical, but they are not all the same. Spherical aberration is a measure of the degree of asphericity they have.

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I will post a link to an article which I think does a pretty good job of explaining it, and listing the amounts of asphericity different manufactures use.

A link to the article "Monofocal IOLs: Impact of Optical Design on Intermediate Vision J. MORGAN MICHELETTI, MD"

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https://crstoday.com/wp-content/uploads/sites/4/2023/08/0823CRST_Alcon-Med-Affairs_Monofocal_Micheletti_ROB.pdf

It seems odd to call something you are trying to achieve an aberration.

I'm going to copy here some quotes on the subjects of aspheric lenses, spherical aberration and related matters. Let's see what we can infer from them:

"Spherical lenses have a constant curvature on their surface, much in the same way that a sphere has a constant curvature (Figure 1a). However, the power of the lens at different points is variable, resulting in relative defocus of more peripheral light rays. Due to this constant curvature, these lenses are easier to make; however, their optics are worse. A perfectly aspheric lens has a variable curvature but a constant power even at the periphery of the lens ... This results in the same focus of all light rays, both central and peripheral. These lenses are more difficult to make, but their optics are better.

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Peripheral light rays are relatively defocused in spherical lenses, resulting in a degradation of image quality. In an aspheric lens, the peripheral light rays are focused at the same point as the central rays, resulting in a sharper, higher-quality image."

My comments on the above:

Constant curvature (spherical) does NOT mean constant power. Spherical cannot achieve constant power from periphery to edge. Aspherical means constant power if it is "perfect". So, when J&J tells us the Eyhance is aspheric but has changing power from the periphery to the center, that's a feature not in common with lots of aspherics.

"SPHERICAL ABERRATION

One difference between the lenses is the approach to correcting spherical aberration. The asphericity of the AcrySof IQ IOL is -0.20 um, which accounts for a precise amount of corneal spherical aberration and is designed to mimic the crystalline lens of a young adult.1 The Tecnis 1-piece IOL has -0.27 um of spherical aberration."

My comment on the above-- I don't WANT my IOL to mimic the crystalline lens of a young adult. A young adult has accommodation. I don't. I need to NOT negate the spherical aberration of my corneas that gives my vision greater depth of field. Example: When I wear distance glasses with monofocal lenses, I have no trouble driving and seeing the dashboard and my phone. I have good depth of field due to spherical aberrations. But if I put on scleral hard contacts it collapses my defocus curve to a spike. I see the road signs better, but I can't read the dashboard and forget trying to read the phone. The contacts take away spherical aberration, I think, and therefore take away depth of field, but give me better image quality at a single distance.

*"Surgeons have come to understand that specific amounts of higher-order aberrations (HOA), particularly spherical aberration, can increase a patient’s overall depth of focus.

*With the finding that IOLs specially designed to neutralize spherical aberration could improve quality of vision, IOL manufacturers began to develop aspheric implants.

*Today, many surgeons implant aspheric IOLs—with negative spherical aberration—to neutralize the inherent spherical aberration of the cornea.

The industry has also introduced aspheric aberration-free implants that are made to preserve the cornea’s preexisting corneal aberration."

*"A variety of factors such as pupil size, total corneal HOA, and corneal asphericity (Q value) affect individual patients’ range of vision with monofocal IOLs, so it is important to note no single lens provides a one-size-fits-all solution.

Ultimately, pseudo-accommodation is relative to the unique features of the patient’s optical system, not just the implant chosen or postsurgical changes."

Here is a graph from an old (2009) article when "standard" IOL meant spherical. It shows how positive spherical aberration in the total eye system gradually increases as we age, apparently from changes in the natural lens, not changes in the cornea as i had thought. And how the total positive spherical aberration jumps up when a "standard" (spherical) IOL is implanted.

More quotes from authorities:

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"Positive spherical aberration occurs when peripheral rays are too bent. Negative spherical aberration occurs when peripheral rays aren’t bent enough"

"we measured the spherical aberration thresholds that produce just-noticeable differences in perceived image quality. The thresholds were measured for positive and negative values of spherical aberration, for best focus and + 0.5 D and + 1.0 D of defocus. At best focus, the SA thresholds were 0.20 ± 0.01 µm and −0.17 ± 0.03 µm for positive and negative spherical aberration respectively (referred to a 6-mm pupil). These experimental values may be useful in setting spherical aberration permissible levels in different ophthalmic techniques. PMID:27699113

Here's a source that contradicts another source I quoted on corneal aberration change as we age. The other source said the lens changes but the cornea stay almost the same. This one says corneal aberrations increase with age as fast as total aberration of the eye system as a whole:

"Results: Both average corneal surfaces show negative conic constant plus higher order aspheric terms Z(0)(4) and Z(0)(6) are significant). These surfaces are misaligned between them and with the line of sight. Such misalignment increases with age as the cornea seems to rotate as a solid body. The apex curvature and the magnitude of the conic constant along the most curved meridian increase as well, but the largest change with age correspond to the aspheric terms Z(0)(4) and Z(0)(6). As a result, the spherical aberration (SA) of the average cornea increases with age at a rate similar to the total SA of the eye.

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Conclusions: The average corneal surfaces are misaligned general aspheres. Corneal SA is higher than total SA, but both SAs increase with age at a similar rate. This confirms that the lens is partially compensating SA and that such compensation is preserved with aging. Misalignment and solid body rotation seem to reduce astigmatism and coma for young and middle-aged corneas."

Here's one I won't quote but instead will post a link for. It's a bench test of 3 IOLs: (1) spherical, (2) aspherical with (3) zero spherical aberration and aspherical with negative spherical aberration. Unlike the bench test that Ron cited giving defocus curves for many IOLs that didn't tell us what sort of simulated cornea (if any) was used in the test, this bench test report tells us something about the corneas in the simulation -- the IOLs were tested using 100 randomly created eye models. The purpose of the test was to find out how the 3 different types of IOL perform if there is tilt or decentration. The result: The spherical and the zero-aberration aspheric did much better than the negative spherical aberration lens when there was tilt and/or decentration in the IOL implantation. https://iovs.arvojournals.org/article.aspx?articleid=2374331 The degradation due to tilt or decentration the negative-spherical-aberration aspheric IOL suffered was reduced depth of field and induced coma (a higher-order aberration).

Here's an article that attempts to decode exactly what is going on in the design of different IOLs. Clearly, there is much more going on than we will ever understand.

*" Posterior surface of Tecnis 1 IOL was spherical and the anterior surface aspherical. In the Eyhance IOL, posterior surface was spherical and anterior surface did not fit to any of our reference surfaces, indicating a higher order aspheric surface design. "

"the wavefront aberration of Eyhance IOL provided by the second surface, had contributions of positive 6th-order and negative 8th-order of spherical aberration"

Clear as mud, right? What it shows me is, there is a lot more to these designs than meets the eye. Or maybe I should say, more meeting the eye than will ever meet our untutored minds.

https://www.nature.com/articles/s41598-022-12694-4#:~:text=the%20wavefront%20aberration%20of%20Eyhance,order%20aspheric%20anterior%20surface%20design.

Dr. Uday Devgan, whose graph of "Spherical Aberration with Age" @jimluck reproduces, also developed a decision tree for helping cataract patients decide between an aspheric IOL with zero spherical aberration or negative spherical aberration. For patients with no prior corneal refractive surgery, the choice comes down to the patient's visual priorities: an aspheric IOL with zero spherical aberration if depth of field is critical; an aspheric IOL with negtive spherical aberration if image quality is critical. If Dr. Devgan is right, then both Alcon and Johnson & Johnson, to different degrees, have chosen to prioritize image quality over depth of field insofar as asphericity is concerned. That the Eyhance achieves greater depth of field than the Alcon monofocals, such as Clareon, indicates, unsurprisingly, that multiple factors are at work in IOL design.

Most of that information seems generally right. I am not sure what you are trying to accomplish with this discussion though. If you want a low net spherical aberration then you should consider the Tecnis 1 which has theoretically zero, if you have an average cornea with +0.27 um of asphericity. The -0.27 um in the lens cancels out the amount in the cornea. If you want more asphericity then consider the B+L enVista which is claimed to a neutral asphericity lens and does not add or subtract any. That would leave you with a net +0.27 um of positive asphericity. And in one reference somewhere that I read a standard spherical lens leaves you at +0.37 um or even more. Our choices are kind of limited. We have to take basically what is "off the shelf". It is a choice though. Probably the more important factor in having increased residual positive asphericity is that the lens becomes more tolerant of position in the eye, and any defects in the eye.

I believe there are some surgeons who may be willing to measure the spherical aberration of your cornea and then help you select the aspherical lens that may best suit your needs. However, that is likely more attractive to the ones trying to shoot for zero overall error.

Have any of you had "corneal topography" performed to better select a lens? That is a special photography technique that maps the surface of the clear, front window of the eye (the cornea).

How much did that cost?

I am thinking that somebody with a fair amount of lenticular aberation might avoid an EDOF lens, since the aberation will provide its own EDOF effect.

I have had a scan done with what I believe was an OCULUS Pentacam, and I have viewed a topography coloured screen of my eye on the surgeon's computer. I believe however the purpose is to measure and identify the type of astigmatism the cornea has. My one eye for example has an offset area rather than a typical bowtie or hourglass shape to the topography. That makes it irregular astigmatism. Could be wrong but I don't think the purpose of the Pentacam is to measure spherical aberration of the cornea. Where I am, the Pentacam exam cost is covered by our public health care. In areas where it isn't I believe the cost is in the order of $100. The Pentacam measurement I believe is used if considering the need for a toric lens. Astigmatism and spherical aberration are not the same thing.

Trilemma,

"Lenticular aberration" will be gone with the removal of the natural lens. Did you mean corneal aberration?

Astigmatism and spherical aberration are not the same thing.

I was mis-using the word lenticular.

I am not thinking of spherical, or cylinder aberrations

I guess the type of irregularity I was thinking of is often grouped into "high order aberrations"

So not symmetric about the sightline (where the center of normal vision is). Not symetric about a plane thru the sightline, as regular astigmatism is.

Did you mean corneal aberration?

Yes. I was misusing the word.

Spherical aberration is an irregularity from the center of the lens to the outside edge. I am sure that it can be measured but I am not sure with what instrument.

Spherical aberration is an irregularity from the center of the lens to the outside edge.<

I think that definition would lead to a lot of misunderstanding. I would think of a spherical lens as having no irregularities because the radius of its curvature is constant from periphery to center. But a spherical lens has lots of spherical aberration; that is why the aberration is called "spherical aberration." It is the name for the inherently poor focus of a spherical lens.

The aberration is that the periphery of a spherical lens always bends light more than the central area, resulting in multiple focal points instead of just one. The spherical lens is perfectly regular but its optical properties are aberrant.

It takes a special kind of aspheric lens to achieve a single focal point. I would call an aspheric lens irregular, because its radius of curvature varies from the periphery to the center. But it can have zero SA if made just right.

Elaborating a bit, an aspheric does not necessarily achieve zero SA. If the periphery of an aspheric lens focuses light closer to the lens than more central areas do (similar to the aberration of a spherical lens) it is said to have positive SA and if the opposite is true (periphery focusing farther from the lens than more central areas do) it is said to have negative SA. An aspheric lens with zero SA is sometimes called "perfect."

An optical system with spherical aberration, (positive or negative) has more depth of field and less contrast than one without SA.

Actually a spherical lens has less spherical aberration than a Tecnis 1 lens. The Tecnis has -0.27 um of SA. The spherical lens I recall has +0.10 um. The enVista has 0.0 SA.