Confused and delaying cataract surgery

I have read all the posts. Thank you! You are helping me more than the ophthalmologist.

Ron, I appreciate your knowledge and willingness to help.

Of course, I have more questions.

I have found two old eye prescriptions:

10/17/2017 RT Sphere; -1.75; -0.50 Cylinder 10 axis.

LT -1.25 Spere and -0.50 Cylinder 175 axis.

02/03/2021 RT -2.50 Sphere; -2.75 Cylinder 073 Axis

LT -2.00 Sphere; 0.00 Cylinder 000 Axis

Current RT -2.75 Sphere; +.75 Cylinder 112 Axis

LT -3.00 Sphher; +.75 Cylinder 164 Axis

So, my question is – if I target the 10/17/2017 prescription would my eyesight be what it was then?

If I target my non-dominate RT eye -1.5 and my dominate LT eye 0.00 – is that mini monovision? Would I need bifocals or trifocals to do my bookkeeping and computer work? If nothing is done to the astigmatism will that help make my eyesight more nearsighted?

I don’t understand the astigmatism minus then plus numbers.

What are the changes in my prescription from? Is this from the change in my hardening lens which affects accommodation? The eye length?

First the easy part. Your current prescription must be from an ophthalmologist. They express astigmatism as a positive value and has to be converted to the more standard optometrist format with negative cylinder. Your current prescription converts to the following:

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Right Eye: Sphere -2.00 D, Cylinder -0.75 D, Axis 22

Left Eye: Sphere -2.25 D, Cylinder -0.75 D, Axis 75

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Most likely the changes in your prescription are due to the cataracts.

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The result of eyes with astigmatism is often expressed as a spherical equivalent. It is the sum of the sphere plus 50% of the cylinder in negative format. So your 2017 spherical equivalents would be:

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Right Eye: -2.00 D

Left Eye: -1.50 D

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If you were to target these values with an IOL your vision would be reasonable similar to what it was in 2017. IOL formulas typically use spherical equivalent in the calculation.

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"If I target my non-dominate RT eye -1.5 and my dominate LT eye 0.00 – is that mini monovision? Would I need bifocals or trifocals to do my bookkeeping and computer work?"

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Yes that would be typical mini-monovision. That is approximately what I have and I almost never use glasses. But, the near vision is good, not excellent. I call it a working vision. When I do fine work with something involving small screws etc. I do reach for my +1.25 D reading glasses. I do not use them for my iPhone or computer though. If this is the way you intend to go, there is likely benefit in the LAL lenses, as each person is a bit different, and they give you the option of fine tuning the amount of myopia in the near eye to suit your needs. It takes the risk out of the surgeon missing the target as well.

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To make a decision on astigmatism you need to know what the computer estimates it will be after cataract surgery. Ask the surgeon for the IOL Calculation sheet. Normally less than 0.75 D of cylinder is not corrected. However with the LAL they may be able to do smaller corrections. In negative cylinder format and using the spherical equivalent formula you can see that astigmatism makes you more myopic. For example your 2017 right eye Sphere -1.75 D, -0.50 D cylinder is a spherical equivalent of -2.00 D, or more myopic than the Sphere alone indicates.

Hi RonAKA,

I have been trying, again, to gather my questions.

I have read so many posts that organizing my questions has become difficult.

One post I read:

Only a very tiny minority of patients can read with monofocals set for distance, that is rare, you are lucky. The amount of near vision people get depends on their eye's natural depth of focus.

Does our eyes's natural depth of focus change over time? Does this have to do with the shape and length of the eye? Oblong in my case? If so, how can you find out what your natural depth of focus is?

There has been discussion on the posts about what the targets are for near, intemdiate and distance vision. Is there a rule? Even though your eye is different from mine, if both our prescriptions are -1.5, will we both see the same?

This is an advertisement for the RX Sight website

https://irp.cdn-website.com/3b8c47cd/files/uploaded/RxSight%20Overview%20-%20Better%20Vision.pdf

It states:

RxSight also enables an EDF procedure that delivers even better UCVA at all distances and minimal vial side effects (IDE Study underway)

I don't know how to find IDE studies.

and

Negative SA (LAL and LDD) extends depth of focus to blend near and intermediate UCVA

I am assuming that Negative SA means spherical abberations. Would this cause Postive dysphotopsia = halos, starbursts, etc? I might have my terms messed up!

With EDF, I don't understand how much actual clear viewing distance I would gain to enhance being nearsighted. Unable to find anything on this on the internet.

My next LAL concern is the importance of the optometrist doing the refraction testing. They have to be excellent. Also, do your eyes change enough that the results might vary from day to day?

Then you have the person operating the Light Delivery Device. How much practice does this person need to be good? How do you ask the opthamologist how many LAL he has placed and is he the only doing the LDD? Does he have alot of experience doing EDF? With the short amount of time I spent with the opthomologist, he mentioned EDF - which I did not get at first because I was used to reading EDOF.

With the LAL, I can't find this information anywhere - does any opthomologist use a target IOL when the cataract is removed and the LAL implanted? I think they always do plano and adjust from there. The recommened healing time is 2 - 3 weeks but I feel I should wait for 6 weeks for complete healing. Therefore, for me to return to work I would ask for a target of RT -1.75 and LT -1.25 like my 2017 prescription. I am assuming my astigmatism will stay the same and that will add to my nearsightedness. I don't think the opthomologist will want to spend time doing all of the measurements. But they will have to if I want my LAL to be with a target. I do have "up close" glasses that are +.5D. I am trying to navigate bookkeeping work while I would wait for the LAL until adjustments. By the way, there are no refrences to patients wanting two myopic eyes.

Tomorrow I am getting contacts to find out if I can handle monovision. I don't have any idea what my prescription will be. I have bad allergies so am wondering if I can tolerate the contacts. The optometrist told me they are much better than 35 years ago.

RonAKA, thank you for your vast knowledge. You have helped me even though I don't totally understand alot..,such as the de-focus curve.

First to be clear I cannot read with my distance set monofocal eye at reasonable reading distances. I can just start to read at about 18-20" or so. Reading would be bad at the normal 12-14". I get my reading from my other eye which also has a monofocal, but is not set for distance. It is set at about -1.60 D. With that eye I can read well and can even see down to 8" in good light. That is how mini-monovision works.

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Yes for sure depth of focus changes with age. At age 45-50 people start to lose their ability to focus closer. It is called presbyopia. That is when people start to need bifocals or progressives to see close as well as far.

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Yes, basically if the outcome of the eye is -1.5 D you are going to see pretty much the same as another person that also is at -1.5 D. There will be person to person differences but in general the refraction is a good measure of your focus distance.

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I don't know that much about the LAL and ability to extend depth of focus. They could give you more astigmatism which would help with depth of focus, but it would also hurt visual acuity. It sounds like it is a work in progress.

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My thoughts would be that if you want to target myopia in the -2.0 D range in both eyes, to get good reading vision, using the LAL lens is probably overkill. Just using a standard monofocal and doing one eye at a time with 6 weeks between them should give you good results. If the first eye is a little off the second eye can be adjusted to compensate. Probably not worth spending the extra $$ on LAL if that is all you want.

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On the other hand if you want to do mini-monovision, LAL is probably a very accurate way of doing it because they can adjust each lens to get what you want.

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If you do not have a LAL surgeon lined up you may want to post at another site called MedHelp Communities Eye Care. There is a Dr. Hagan there that is quite helpful and based on his posts his clinic does LAL. He has recommended clinics in other cities for posters that do LAL.

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With your contact lens trial you should get your dominant eye corrected as close as possible to plano, and your non dominant eye left at -1.50 D on a spherical equivalent basis. That is your sphere plus 50% of the astigmatism. The contact lens fitter should know about that.

I do understand that your reading vision is from your monofocal set at -1.6D.

I did not have luck with the contacts today. I don't know what the target was because

my vision did not change much from the way that it is now. Because the cataracts are too bad. This optometrist is also the doctor that does the refractive exams for the LDD adjustments. I don't think there is a way for me to try-on mini-monovision.

I have also seen a second opthomologist at Discover Vision, Dr. John Doane, in Kansas City. He is in the same practice as Dr. John Hagen. Dr. Doane did my husband's Lasik surgery 25 years ago. I think I will make another appointment with Dr, Doane to see if he can help me navigate the LAL process. He did tell me when I had my appointment that some of his patients have said they have the best vision in their lives.

I did find more information on EDOF:

The Monofocal IOL With a Twist

A misconception about the LAL is that it’s a simple monofocal lens aimed at precision distance vision. While this is partly true, it’s also highly oversimplified. It is indeed a monofocal lens; however, given its aspheric design, it does allow for an element of extended depth of focus (EDOF). This aids in extending visual range even in a plano targeted eye. Additionally, patients can elect to add negative spherical aberration to their nondominant eye during the light treatments. This adds an additional 0.50D-0.75D of EDOF, providing a solution for presbyopia and reducing the need for reading glasses postoperatively. In our practice, we have strayed away from the term “monovision” as it implies full ocular independence and loss of binocular balance. Instead, we use the term “blended vision” because there is substantial overlap between the eyes, allowing for binocular summation for maintained depth perception. About 80% of our patients choose some form of blended vision, with the nondominant target being -1.00D to 1.25D on average. The beauty of the LAL is that we can customize the near target based on lifestyle. The added EDOF of the nondominant eye still preserves usable distance visual acuity. Even with a -1.25D target, a healthy patient can often maintain 20/30 or better unaided distance visual acuity without glare or halos.

I ask: "This adds an additional 0.50D-0.75D of EDOF "- how does that translate into what a person sees?

Once again, thank you !

Curiously, the Premium Vision Surgical Centres in Ontario, whose website promotes both the Eyhance and Light Adjustable IOLs, uses "blended" in its Eyhance discussion: "Eyhance Blended Vision is similar to conventional monovision (MV). Both methods involve correcting the dominant eye for distance vision, while the non-dominant eye is corrected to be slightly nearsighted for near vision. Unlike monovision, EBV offers a greater range of sight (focal depth) in both the dominant eye and the non dominant eye. The advanced design of the distance Eyhance lens allows it to offer vision throughout far and intermediate ranges, reaching as close as 60cm away. This is complemented by the near eye’s ability to see from a meter away, to as close as 40cm. Together, these lenses overcome the weaknesses of monovision by covering the entire range of vision, from distance up to 40cm, without creating a Blur zone in the middle. Essentially, this new Blend Zone makes it easy for the brain to merge the images of both eyes thereby achieving true binocular vision. Overall, EBV helps adaptation and depth perception...."

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My point is that the proposed virtues of the LAL IOLs can be at least approximated at substantially less expense. That said, if one can afford and chooses to pay for the LAL solution, I wouldn't doubt, but don't know enough to endorse, claims that it offers some greater likelihood of success.

I think that quote involves some degree of exaggeration and is overall misleading. There are a number of lenses that use spherical aberration to give some EDOF effect to a monofocal. The B+L enVista does it, as well as the Eyhance. But the gain is modest if distance vision is not impacted significantly. It is more in the order of 0.25 D gain, not 0.5 to 0.75 D.

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I think the "blended vision" is more marketing hokey pokey. To get to the point of being eyeglasses free with the LAL you need to use mini-monovision. They are just changing the name of it to make it sound different. Mini-monovision has a significant degree of overlap and does not compromise depth perception, unless you go with a differential between the eyes of more than 1.75 D or so. This marketing is similar to the Lasik surgeons who promise to "fix" your eyes so you can see close as well as far like you are young again. What they are really doing is mini-monovision, but with a laser.

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I would take that stuff with a grain of salt. The real advantage of the LAL is being able to adjust the power after implantation. Since you were not able to use contacts to simulate mini-monovison that would be a big upside for you IF you are going to do mini-monovision. It would let you test it out to see how much differential you like after they are in your eyes. The other advantage of the LAL is that they can correct astigmatism to a degree with it. That will give you clearer vision. It is better to get more depth of focus with the sphere power of the near eye, than it is to stretch it with astigmatism. Like using positive asphericity it does make a modest increase in depth of focus but with a visual acuity penalty.

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But, I say "IF" because there is no real advantage to LAL if you only plan to do both eyes myopic in the -2.0 D range. The surgeon will have two chances to give you that using just plain old monofocals.

If I understand correctly, RonAKA calls -1.6 D monovison when you have the near eye 1.6 D nearsighted . I lean toward defining that to mean the difference in diopters between the far and near lens. Since it does not seem to be (AFAIK) clearly defined authoritatively, we can choose.

There is a word you can find in the technical documents: anisometropia , which is measured in D (diopters). That word corresponds to my preferred way of defining monovision. If you use that word in some Google searches, I think you will find some technical papers on the subject. And using anisometropia monovision as a search term is really going to find papers on that topic. But they will not be the easy-to-read stuff. I think that it comes up in a paper that includes "Optimal amount of anisometropia for pseudophakic monovision" in the title, and RonAKA cited it recently in my "I was wondering where you draw the line between monovision and mini-monovision (1.5 may be it)" thread. Incidently, pseudophakic is not that useful of a word IMO. I think of it as roughly meaning IOL, but used as an adjective.

There are also studies on the advantages of having the dominant eye be the far-focused eye for monovision. My recollection is there is not much downside to having the dominant eye being the near eye. There is a term for that too, but I don't plan search it out unless you want it and could not find it.

The American Academy of Ophthalmology (AAO) measures the amount of monovision in terms of the amount of anisometropia (the difference in the refractive errors between the two eyes considered as spherical equivalents). See (available on the web) AAO Cataract in the Adult Eye Preferred Practice Pattern (P29) (distinguishing between "modified monovision (-0.75 D anisometropia)" and "conventional monovision (-1.75 D or more anisometropia)").

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Also, according to the (available on the web) AAO Refractive Surgery Preferred Practice Pattern:

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"Distance correction is usually performed for the dominant eye and near correction is performed for the nondominant eye. (fn. omitted) Evidence exists to suggest that near correction in the dominant eye may also be successful and even preferable in some patients. (fn. omitted) ... A preoperative trial with contact lenses is a useful test to determine the desired refractive endpoint for each patient based on the intended refractive outcomes." (P104)

I think "pseudophakic" is the technical way of saying "fake" or "artificial".

I think you have to be careful with the context of that article "Optimal amount of anisometropia for pseudophakic monovision". I recall it assumes the distance eye is at plano. So when they speak of an anisometropia of 1.5 D it means the close eye is at -1.5 D sphere. The purpose of monovision is to give a full range of vision. To do that the distance eye has to be at plano or 0.0 D or very close.

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No if the surgeon misses and you end up at -0.50 D in the distance eye, yes, you could accept that reduced distance vision and then target -2.0 D in the near eye. You would avoid the negative effects of too much anisometropia, and get better near vision, but you would also likely fall short of 20/20 distance vision. But it may be an option if the first eye turns out to be a little less than perfect.

Thanks. With RxLAL, I expect the dominant far eye to not have much of a miss from target. I know there will be some. I have not yet selected a target, but -.5 and -.25 both seem like useful targets. My thinking is that -0.5 D still gives good vision at infinity, but when driving, most of the important stuff to see, looking ahead, is beyond 4 meters (13 ft).

I went back to the paper. I found the "Method" either ambiguous or too hard for me to understand. The "Conclusion" does not seem to make an assumption, that the far eye is adjusted to plano. Instead it just refers to " Pseudophakic monovision with anisometropia", which to me implies the difference in focus between eyes.

With the LAL I is see no reason to target something other than emmetropia in the dominant eye. Targeting -0.25 or -0.50 is only used as a factor of safety for a miss by the surgeon on the correct power. With the LAL there should be no miss after a correction or two. You may be interested in this article. It is not as useful as the "Optimal amount of anisometropia" article but is worth a read. A quote from it:

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"In our practice, the target refraction is emmetropia (0 to −0.5 D) in the dominant

eye and slight myopia (−1.0 to −1.5 D) in the non dominant eye"

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I am guessing they are not using the LAL and that range of 0.0 to -0.50 D is to avoid a miss to the far sighted side.

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Clinics in Surgery

1 2018 | Volume 3 | Article 2027

Monovision Strategies: Our Experience and Approach on

Pseudophakic Monovision Published: 16 Jul, 2018

Misae Ito CO* and Kimiya Shimizu

Even if we were to assume no risk of being off after adjustment, I expect things can drift with time. I don't know the accuracy and resolution of the RxLAL adjustments.

And my other thought was that if I got a perfect -0.25, I could still have 20/16(? )(LogMAR -.2) at infinity. However I am not sure. In "Comparison of dynamic defocus curve on cataract patients implanting extended depth of focus and monofocal intraocular lens" on the NIH site, the fig 2a defocus curve green line seems to be for a plain IOL. I am confuse with dynamic vs static in this context. And since ZXR00 seems to beat monofocal at all points, maybe I should distrust this graph. I would also expect the LogMAR of a monofocal to be better than zero at its optimum. So I suspect that this study was paid for by J&J TECNIS.

I would like to see a defocus curve for a monofocal lens, where the study is from an independent source. How common are truly independent studies on IOLs?

The accuracy of the LAL adjustments should be very good, and in fact more accurate than eyeglass lenses which come in 0.25 D steps of power. With a skilled surgeon I would expect even better with the LAL. Keep in mind they get at least 2 or 3 chances to get it right. With a standard monofocal you roll the dice once and hope for the best. That is why a margin of error is factored in. You target -0.25 D but really hope it turns out at 0.0 D.

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There is nothing "perfect" about -0.25 D for the distance eye. Achieving 0.0 D will give you better distance vision than -0.25 D. I am not sure it is reasonable to expect 20/15 out of your distance eye, although some may do that. 20/20 is a more reasonable expectation especially on a monocular basis. With mini-monovision keep in mind that you are getting your distance vision with one eye only. Many times defocus curves are displayed on a binocular basis -- or in other words using both eyes both set for distance. That will always be a bit better for visual acuity, and you won't achieve that with mini-monovision.

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If you want to see a basic defocus curve google Vivity Package Insert. They compare the Vivity lens to their basic monofocal and show the defocus curve for both. I think they are realistic curves. Just watch the monocular vs binocular in the fine print.

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For another one google this article, and see figure 10. It looks quite realistic for a standard monofocal compared to the Eyhance. It shows the monofocal being better at the 0.0 D peak visual acuity point, and then closer up past -0.5 D the Eyhance has a flatter down slope. This figure 10 is said to be a monocular curve.

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Unaided Intermediate Vision: A Paradigm Shift in Cataract Surgery? DR JAY YOHENDRAN 1ST MAY 2020

In the study, "Under Conflict of Interest," it said nothing about being funded by J&J or anyone else.

Good point. But somehow I am suspicious of an EDOF lens giving better visual acuity at the best focus point than a non-EDOF lens.

I suppose it depends on what you mean by common. But peer review provides at least some protection against researchers' associations with manufacturers biasing their published results. Here's an example of a peer-reviewed article by authors who say they have no conflicts of interest and received no financial support or sponsorship:

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Sonan Yangzes, et al., Comparison of an aspheric monofocal interocular lens with the new generation monofocal lens using defocus curve, Indian Journal of Ophthalmology 2020.

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And here are some examples of peer-reviewed articles by authors who do disclose financial support or sponorship:

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Aixa Alarcon, the lead author on Optical bench evaluation of the effect of pupil size in new generation monofocal interocular lenses, is identified as a Johnson & Johnson employee. BMC Ophthalmology 2023.

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Similarly, Johnson & Johnson is disclosed as having participated intimately in a study published in 2020 as Clinical evaluation of a new monofocal IOL with enhanced intermediate function in patients with cataract in the Journal of Cataract and Refractive Surgery, the official journal of the American Society of Cataract and Refractive Surgery and the European Society of Cataract and Refractive Surgery.

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Less intimately, J&J supported the study behind the following article with a research grant. On the other hand, the lead investigator, Mayank Nanavaty, also discloses having received research grants from Alcon and other manufacturers as well: Visua Acuity, Wavefront Aberrations, and Defocus Curves With an Enhanced Monofocal and a Monofocal Intraocular Lens: A Prospective, Randomized Study, Journal of Refractive Surgery 2022.

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In contrast, there's been some discussion here about an Alcon-sponsored video presentation at a recent conference by an ophthalmologist in private practice who concluded that Alcon's Clareon monofocal produced substantially similar visual acuities to the Johnson & Johnson Eyhance. In addition to features in the way the work was done that may have biased the result in favor of Alcon, I'm not aware, at least as of yet, of the underlying 'study' having been published in a peer-reviewed journal.

I have just come to that same conclusion. With the LAL the only advantage would be the ability to try on monovision. Anytime a lens gives you EDOF you will lose visual acuity. If I decide to implant the LAL, it will be because I want to try mini- monovision vision. My husband drew me a graph with diopters on the y-axis and inches on the x-axis and what I discovered is that EDOF does not give you very much in improved depth of focus JUST A FEW INCHES 3.6 inches between- 2.5 D and -2.0 D. Then I came to the conclusion, that if you take the EDOF too far you probably end up with dysphotopsias. I am anxious to hear from RonAKA to see if my conclusions are anywhere near correct! If so this is truly an aha moment.

Yes, EDOF does compromise distance vision to a degree. You can see that in the Vivity Package Insert pdf document where the defocus curves of the Vivity are compared to the standard monofocal (AcrySof IQ I think). J&J say their Eyhance does not do that, but that defies science. I think they are really saying it does not degrade distance vision significantly. But, it also does not extend the depth of focus significantly either. Vivity does about 0.6 D more than a monofocal, while the Eyhance does about 0.30 D more. The learning in this is that an offset of a monofocal in one eye can quickly do more than just an EDOF lens. Just an offset of 0.75 D (micro-monovision) will give more near vision than a Vivity set to plano for example. And with the Eyhance only 0.25 D offset does about as much as the lens itself.

trilemma

There are studies and there are still more studies in every area of medicine, and you can easily get lost in cyberspace rabbit holes reading one study after another. This is especially true if you are are a layperson like those of us here. I have worked in hospitals for many years and even physicians have told me that it's very difficult to sort through the sheer volume information that is available now. You just have to do the best you can and hope for the best.

With the LAL the only advantage would be the ability to try on monovision.

I think the main advantages of LAL are

1. a potentially finer granularity of prescription. Some toric IOLs only come in cylinder in 0.5 diopter steps.
2. ability to compensate for any miss from target. I may expand my priority list.

Also, there may be some tolerance in the axis of the toric lenses in implant, and I think the needed axis could shift in the first weeks.

What I don't know is the step size (granularity) of the RxLAL tuning for cylinder and spherical. You would think it would not have steps, but it may be that the software for the light delivery device has some granularity. Indeed, "The RxSight Light Adjustable Lens" By Mitchell A. Jackson, MD September 1, 2022 says

The LAL corrects in 0.25D increments of sphere and cylinder (twice as precise as standard premium IOLs) and corrects down to 0.5D of astigmatism. With customized blended vision, LAL patients can achieve excellent vision at all distances without the glare and halos associated with multifocal IOLs. In fact, 75% of LAL patients select blended or monovision.

Have things changed since then? I don't know. But still, 0.25 increments is better than the standard toric IOLs.

I do not plan to try out two different monovision amounts. But if I did pick a number that I expected to stay with, I could see opting for a change. Sounds similar, except that I would not necessarily intend to try two and then pick one. I am not saying that is wrong, but I don't plan to do that.,

I am forgetting all about EDOF and going to focus on Mini monovision. Now, I I need to understand how good a silicone lens is.

Silicone is not a popular choice for a lens material. That may have some basis in early experience with the material where it was found to be susceptible to deposits on the lens which impaired visual acuity. However, it may have improved and I see that the LAL IOL uses silicone. You would have to search for articles on the long term experience with the LAL lens to see if these issues have been solved.

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Silicone has a lower refractive index than the much more popular hydrophobic acrylic material used by Alcon (AcrySof IQ, Clareon) and J&J (Tecnis 1, Eyhance). This means the lens is thicker and is closer in thickness to the natural lens which gets removed during cataract surgery. Some feel there is an advantage to that in avoiding positive dysphotopsia. Other studies contradict the theory that high index lenses are a problem. Being thick has some down sides as a larger hole has to be poked in the eye to get the lens in, so recovery time may be a little longer.

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I think if you are considering the LAL which has some real advantages in the getting the accuracy in a mini-monovison application I would focus on what studies have been done on the long term use of the LAL lens to see what the experience has been. I think it has been in use longer in Europe than in North America, so there should be data on it. It was not an option for me when I was choosing a lens in Canada so I have not done a lot of looking into it.

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You can google this article for a comparison of IOL materials. Some of the data and conclusions and data in it may be dated even though it has been reviewed recently.

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EyeWiki Comparison of IOL Materials Article initiated by: Jeremy Kudrna, MD, Rucha Borkhetaria, BS, Clever.Nguyen

RonAKA, with EDOF of 0.5D - 0.75D in the LAL adjustments, would I be able to be corrected with eyeglasses if necessary? I don't know how much EDOF the LAL has before any adjustments. As always, thank you for your help.

I have not seen any convincing evidence that the LAL has any EDOF. I have seen statements that they are investigating it, but no evidence they can do it. I think they could do it by leaving or even enhancing the amount of astigmatism. But, having astigmatism, I think that is a poor way of doing it. It costs you in visual acuity. But on the other hand if you can accept they are doing it, and the astigmatism is symmetrical then yes eyeglasses should be able to correct it.

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I believe the LAL is basically a monofocal lens that can have some (2 D?) of astigmatism correction added to it.

From the article about a twist on the LAL: The surgical target should be set for plano with both eyes regardless of the final refractive target. This allows for re-establishment of eye dominance postoperatively and allows room for the added negative spherical aberration to enhance depth of focus in the nondominant eye.

At my eye appointment, I asked to have both eyes targeted at -2.0 and my surgeon explained that if I did not start out at plano, I would miss the EDOF created by the first adjustment. He does not want me to "miss this experience". To my way of thinking, if I start out where I think I should be - there will be more adjustments to fine tune mico and mini monovision. I need to email my surgeon and ask how much EDOF there is in the LAL. However, maybe you have figured out the EDOF is actually an astigmatism.

Also, it seems if you have EDOF and mini-monovision you will have a loss in visual acuity.

Yes, if they can predictably add positive asphericity it should give increased depth of focus without impacting astigmatism. B+L with their enVista lens does this to increase the lens tolerance to being potentially off center or tilted in the eye, and as well increase the depth of focus somewhat. They publish the graph below which shows the residual asphericity compared to other lens options. J&J with their Tecnis 1 use a lens with -0.27 um of asphericity to theoretically reduce asphericity to zero. It also results in the least depth of focus, and would be more sensitive to lens position in the eye. Alcon with the AcrySof (and Clareon) target some positive asphericity as they believe that is the optimum based on studies they have done. EnVista has no asphericity correction and leaves you with -0.27 um of positive asphericity. According to my translation of the Eyhance data I put a red dot on this graph where I thing the Eyhance falls on this curve of visual acuity vs depth of focus. As you can see the more positive asphericity you have the larger the enhancement of depth of focus, but also the larger the loss in visual acuity.

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I can't comment on how they do this or the best way to get there. I think you would be best to listen to their advice on that. But, to be clear this is a potential option to increase depth of focus with a cost in visual acuity loss with asphericity. Increasing astigmatism is kind of like half doing the same thing but with only two quadrants of the eye.

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My conclusion based on using the Vivity for increased depth of focus vs a monofocal is that there is no real great benefit if you can hit the targets of -0.25 D or ideally 0.0 D in the distance eye and -1.50 D in the near eye. The key is hitting the targets, and with the LAL that should be easily possible.

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As a curiosity point some 10-12 years ago the new wave in IOLs was aspheric IOLs like the Tecnis 1 and AcrySof IQ. They have essentially replaced the spheric IOLs which were the norm before that. They result in a positive asphericity of 0.37 um and as you can see from the graph offer even more depth of focus than the enVista, but at a further drop in visual acuity. Visual acuity seems to have won out, as now the spheric IOL is only used in third world countries commonly, but possibly in North America too if you really looked for it.

Yes, if they can predictably add positive asphericity it should give increased depth of focus without impacting astigmatism.

I don't understand this statement.

Asphericity is essentially a change in the power of the lens based on the radial position away from the center of the lens. In other words the power is not the same in the middle of the lens as at the edge of the lens. But, it is uniform around the circumference of the lens.

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Astigmatism measured in cylinder diopters is when the power of the lens/cornea changes based on the angular position around the eye. It is basically when the cornea is not spherical but oblong shaped. If you look at the eye from the front and think of it like a pie divided into 1/4 sections then two opposing quadrants will be of a different power than the adjacent two opposing quadrants. If you get to look at your topological map of the cornea after your eye exam and have astigmatism you should see an hourglass or bowtie shape to the colours indicating the areas with different slopes (powers). In regular astigmatism these areas will be symmetrical. Irregular astigmatism is when the areas of different slope are shifted off to one side or are not symmetrical like a bow tie.

Thanks. So an implication of this definition is that Asphericity does not have a 0 to 180 degree axis, whereas astigmatism.

If you Google "printable astigmatism chart", you will find various charts with lines at different angles around the center. If you have significant astigmatism, when viewed at a distance with one eye, the lines will appear darker on one axis and lighter at right angles to that.

Yes, that probably is an indication of lines being more or less in focus with the lines appearing narrower when in focus.

So what is positive asphericity? Is that when they make the center of the lens more curved so that your close vision improves when the light is bright, and your pupil stops down, and you are reading. I know at least one of the EDOF lenses does it that way.

I am skeptical that the light would generally be brighter if I was reading something closer. I guess I could darken the room when watching TV and use a high-intensity reading light.

This is a rather complex subject, and I have never really taken a deep dive into fully understanding it. However this article may answer your questions. Since it is a .org link I will try posting it rather than naming the article.

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https://www.eyeworld.org/2018/understanding-spherical-aberration/

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I find figure 1 quite informative. It basically says with zero asphericity all the light from the center to the edge of the "lens" is focused at one single point. I put lens in quotation marks because it really is the total effect of the cornea and the natural lens before cataract surgery, and the cornea plus the IOL after cataract surgery. The two other figures show that negative asphericity is like being partly far sighted. The light from the outside of the lens gets focused behind the retina and is kind of useless as it will only help at distances beyond infinity. In the c part of the figure the effect of positive asphericity is shown. This indicates that light from the outside of the lens is focused short of the retina like being myopic. Myopia helps you read at closer distances when the lens is not at its prime distance.

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So I think the sum total of this is that in lower light conditions that includes more light from the outside of the lens will help you see when lighting is marginal. This is of some benefit, but the bottom line is that the improved depth of focus becomes light dependent.

Ok, I got sucked in. dot org sites still get sent to moderation. You will have to wait till tomorrow or later when the folks across the pond come back to work...