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The Pros and Cons of Mini Monovision

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RonAKA
RonAKA

In view of the recent posts with misinformation about Mini-Monovision I thought I would post my experience with actually having Mini-Monovision. I first used monovision when I was wearing contacts for distance vision and I got to the age where presbyopia started to become an issue. Taking contacts out to read, and then putting them back in again, is not really a viable option, so with the help of a contact lens fitter I set one eye up for closer vision and the other for full distance. It worked very well for me, but with all of the issues associated with wearing contacts. I did it again for about 18 months after I got my first cataract surgery with a monofocal IOL set for full distance, and used one contact for the near eye. That worked well, so I proceeded to do it with my second eye using an IOL. I ended up at -0.25 D in the distance eye and -1.40 D in my near eye. Astigmatism compromises my vision a bit in the near eye, but all in all I am extremely satisfied with the outcome. I would not hesitate to do it all over again. The only thing I would do differently would be to get a toric in the one eye that turned out needing it. So what are the Pros and Cons of doing it?

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Cons:

  1. First you have to accept a slight decrease in distance visual acuity as at full distance you will not have much binocular summing effect. My distance eye alone is 20/20+. If both eyes were done for distance, I expect my binocular vision would be 20/15. So, I did give up half a line of visual acuity.
  2. From my minimum distance of vision at 8" out to 18" I do not have much binocular 3D vision. I have threaded a needle, but I think if one was sewing for hours, some +1.25 or so reading glasses would make it easier. From 18" out to 7 feet or so, I have very good binocular vision. I would expect that monovision would not make for a good excuse for swishing on a tennis or golf swing.
  3. For reading very fine print in dimmer light you will likely need reading glasses, or a light. I use some +1.25 D readers perhaps once a week or so. I don't bother bringing glasses with me when I go out shopping or pretty much anywhere. I have had no trouble reading menus in dimly lit restaurants. I may put readers on momentarily once a week or so, for a particular task. But, they come off immediately as I dislike looking at anything of any distance with them on.
  4. I drive at night in the city, but for safety purposes I do wear a pair of prescription progressives when I drive out of the city on dark roads at night. I worry about a deer or moose coming out of the ditch and not having time to see it. I may wear my prescription glasses once a month or so.
  5. You may have trouble finding an Ophthalmologist that will work with you to get properly fitted with the correct IOL powers to achieve good monovision. Some just do routine distance vision in both eyes without even asking what you want. Some seem unaware of how it works. And I don't like to play the conspiracy theory card, but I suspect some find the "premium" lenses much more profitable than doing monovision. Monovision just needs standard monofocals which are the lowest cost and I'm sure the least profitable for them.
  6. If you have difficult eyes with prior laser surgery, or are at the extremes for myopia or hyperopia, it can be more difficult to hit specific refraction targets needed for monovision. In this case your will want to have a surgeon that will be very careful selecting IOL Power formulas, and making sure the power is as correct as possible. You may also want to consider surgeons that use the Alcon ORA system to measure the power during surgery to ensure higher accuracy.

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    Pros:

  7. Aspherical monofocal lenses bring all the light to a single point and for that selected point give the highest visual acuity. With a monofocal each eye is set to a different distance. Normally the dominant is set for distance (0.00 to -0.25 D), and the near eye set for -1.5 D, or about 2 feet. This gives the brain two options for vision, and with each eye there is quite a wide range of distance they are still effective at while being off peak. The brain does a good job of blending the images together as one.
  8. Compared to multifocal (MF) lenses and extended depth of focus (EDOF) lenses an aspheric monofocal has a high contrast sensitivity at the peak focus point. So this gives maximum contrast sensitivity in the distance eye at night for driving, while the other eye can provide maximum contrast sensitivity up close, like when reading a menu in a dimly lit restaurant.
  9. Monofocal lenses, unlike MF and EDOF lenses have very minimal optical side effects like halos, flare, and spiderwebs around point sources of light at night.
  10. Monofocal lenses have the lowest price and in many jurisdictions it is at no cost. This compares to MF and EDOF lenses which have a premium price in the range of $5,000 to $6,000 a pair.
  11. If the focus point differential between the eyes (anisometropia) is maintained in the 1.25 to 1.5 D range there is minimal impact on the ability of the brain to blend the two images. In the past some have used full monovsion with anisometropia in the 2.0+ range. This gives better reading, but at a cost. This practice has been pretty much abandoned in favour of mini monovsion (1.25 to 1.50 differential).
  12. With MF and EDOF lenses you kind of roll the dice and hope to get what you expect. If you do not and are unhappy with the outcome, it may be more difficult to correct the issues with eyeglasses. You can't get eyeglasses that will undo the multiple focal points built into a MF lens, or unsmear the stretched focal point of an EDOF. However when you use monofocal lenses to do monovision your eyes are easily correctable with eyeglasses. Prescription glasses are always a safe plan B that can be counted on.

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    Summary

    My experience is that Mini Monovision is one of the "Best Kept Secrets" in the Ophthalmology field. Some can't be bothered to tell you about it. Some don't seem to know much about it. Some don't want to be under pressure to hit a specific target for myopia in the near eye. And, unfortunately some only want to do premium lenses with their associated higher profit margins.

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    I would suggest if you are interested in mini-monovision there are a couple of critical questions to ask when looking for a surgeon. One of course is to ask if the surgeon does monovision and is willing to work with you on it. The other is to ask what brand and type of lenses does the surgeon use. Some a locked into one specific manufacturer, and others are locked into premium lenses only.

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    And for those that suggest monovision is unnatural consider that man has been around for about 200,000 years, while eyeglass correction has only been available for less than 1,000 years. Our brain has evolved to use the images from two eyes and put them together for the best combined image. And also consider that it is not only used for IOLs, but it is also commonly used with contacts, and also with Lasik surgery to get closer vision. They don't use Lasik to give you a multifocal eye, they use it to give you monovision using two eyes.

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    I hope that helps some, for those who are considering this Best Kept Secret option for IOLs.

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  • joseph54594
    joseph54594 RonAKA

    Edited

    I had monovision in June and with a lot of written emails, they still got it wrong. tying to calculate by how much and remembered you knew how to calculate. My right eye lens was set to +18.25. target was .5. I don't know if that means they are .25 or so off or way more. Can you calculate how big a differnce it is between .5 and 18.25? It was an over correction, which most would say is good, but my left eye for close had to be undercorrected and that isn't what I wanted my left eye targes was +2.5 and is at +20.0 , so a .5 difference, which I heard is to be expected that they can be off + or- by up to .5. But, I suspect he had to compensate for over correcting my dominant eye and it was more than than he missed it because I paid more for the measurement tool. Can you tell how much the diopeter difference is now +20.0 and +18.25D? thank you!

    • RonAKA
      RonAKA joseph54594

      Edited

      The basic thing that needs to be understood is that when they remove a cataract, they remove the whole natural lens. That lens has a power of about +18 or +19. So that lens removal has to be compensated for by having an IOL power in that range to replace it. That is why there is so much difference between the IOL lens power and an eyeglass lens power.

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      Besides correcting for the removal of the natural lens the IOL has to also correct error in the cornea and any offset you want from plano vison. When you mix all those requirements together you really cannot tell anything from your IOL lens power other than you must have had quite good vision befor cataracts. If you were very myopic or near sighted the lens power would have been much lower in the range of +12. And if you were far sighted the lens power would be in the range of +26 or so.

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      What you really need to know to understand what is going on is to get an eyeglass prescription. That is the test where they ask you "which is better, one or two?". IOL targets are set based on what eyeglass power will be needed to correct you to plano. The normal practice for mini-monovision is to target -0.25 D in the distance eye, or very slight myopia or near sighted, and -1.50 D in the close eye, modestly near sighted. So if you could post your eyeglass prescription from at least 5 weeks after surgery I could comment on where you ended up.

  • RonAKA
    RonAKA

    Edited

    Another participant here, Julie, was kind enough to give me the link to a Mayo Clinic Webinar that discusses the clinic's experience with the Light Adjustable Lens, LAL. This video is interesting in that nearly all the patients that select the LAL do it with the intention of implementing mini-monovision or as LAL likes to refer to it, "blended vision". It is just another name for the same thing.

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    It is worth watching this whole video if you have interest in mini-monovision or LAL. The advantage that LAL has is the ability to more accurately hit the ideal targets for mini-monovision, and refine them based on personal preference. I think what people choose is very relevant for those doing mini-monovision with monofocal lenses. Here are some interesting points that I saw in the video:

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    7:40 - This is a discussion about the value of mini-monovision (blended vision), and the number of patients that select it. A comparison is made between those that select mini-monovision and get 20/20 vision for both near and far to those who select the Panoptix multifocal lens. 80% of the mini-monovision patients achieve the near and far 20/20 vision, while only 40% of the PanOptix patients achieve it. That is a major difference.

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    22:18 - This is the start of an interesting section on where patients start with their target refraction and how it evolves over their three available steps (in a couple of cases 4 steps) of refinement. In the distance eye everyone goes for plano of course to get their 20/20 distance.

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    23:14 - This is the beginning of the section on near eye choices, and probably the most interesting. Most start at -0.75 to -1.0 D. With two exceptions where the patients decided to return to plano, the rest converged with choices in the -1.3 to -1.50 range. To me this is a high endorsement of the standard recommendations for mini-monovision to target plano in the distance eye and -1.50 D in the near eye. For those using standard monofocals with the reduced accuracy of hitting the target compared to the LAL, the "plano" target with a factor of safety to avoid going far sighted is to actually target -0.25 D. Here is a screenshot of the graph showing the progression of adjustments for the near eye.

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    image

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    The link to the full Webinar is:

    https://medprofvideos.mayoclinic.org/videos/light-adjustable-lens-what-every-ophthalmologist-should-know-webinar

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    Hope that helps some with those debating what the correct targets for mini-monovision really are. This is what people choose that get 3-4 do-overs!

    • phil09
      phil09 RonAKA

      Edited

      Yes, good stuff, RonAKA. A few questions and comments:

      • I see only 7 LAL patients charted at 23:14. Is that all the experience Mayo has? It's still informative, but I would love to see them report back after they've done 50 LAL patients.
      • Reading that graph, I see a wider range of near eye targets: -1.3 to -2.0. The median (excluding the two outliers) is -1.5, though it's the median of only five observations.
      • I speculate that there may be more than one "right" monovision target for cataract patients - perhaps one for patients who are already experienced and comfortable with monovision, and another for patients who are new to monovision when the first get their LAL or other IOL. LAL patients only get a few weeks of adjustment time before they must lock in a prescription - maybe that's not enough time to get comfortable with a larger anisometropia gap between eyes. Perhaps somewhat greater anisometropia would serve patients (or some patients) better in the long run. Perhaps not. As I say, I'm speculating, and have seen no good data, just an anecdote or two.
      • I could not make head nor tail of the line graph shown at 25:00 on the right side of the page. The monofocal and toric data are clear enough. But the LAL results, and Dr. Mahr's comments, are pure gibberish to me. How is it a good thing that 75% of LAL patients were expected to potentially gain ZERO letters after surgery (the yellow line in the chart), when 75% of the conventional lens patients gain up to 10 letters? Why would aphakia produce results in the lower-right corner of the graph - where zero percent of patients gain 50 letters? How can actual LAL results be a green triangle - this is a line graph, don't the results have to be a line in order to make any sense? Am I misunderstanding, or is this chart complete nonsense?
    • RonAKA
      RonAKA phil09

      Edited

      I have to admit that I really do not like video presentations of data because it is so hard to search them quickly for details like you are asking. The data presented seems to be a limited number, but I see in the summary that this is supposed to be based on their first year of use of the LAL procedure. I would expect there must be many more cases that what is documented in the graph. I have a recollection that one question was asked near the end of the presentation about how much experience there was with the LAL, and a very small number (fraction of 1%?) of the procedures in the US were done with LAL. I just can't remember if there was any reference to the number that the Mayo Clinic has done.

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      I think the value of this data is in what people choose when they have options to try out for real. The preference is personal of course, and I see one patient opted for -2.0 D. I think looking at this is helpful for those picking a target for monovision with plain monofocals. We can benefit from the experience of those who have paid $10K plus to use the LAL!

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      I also could not make sense of those complicated graphs that I think were intended to show how much better the LAL is than standard non adjustable lenses in achieving desired targets. I also did not spend much time trying to figure it out either. Seems obvious to me that an adjustable lens would be better than a non adjustable lens. When Dr. Mahr was introduced the moderator said he was a specialist in doing "big data" research in cataract surgery outcomes. Perhaps that is what is behind the overly complicated analysis.

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      What kind of amused me was that this Dr. Mahr is obviously using progressive lenses to get near vision and you can see him holding his head up as is forced by progressive lenses to read his prepared script for the presentation. I was thinking he would benefit personally from mini-monovision! But, not likely at cataract age yet...

    • phil09
      phil09 RonAKA

      Posted

      I agree about disliking video for stuff like this, and I did not mean to give you an extra assignment! I had not yet had a chance to view the entire video, but intended to do so.

      • At 8:00, they do show that the range of -1.3 to -1.5 D is actually based on the outcomes for 103 patients from FDA data. I don't know how representative a sample this was, but it is certainly large enough to be meaningful.
      • I agree that the LAL patient preferences are telling. I think I want more than -1.5 D myself, but it would be great to be able to try it out before deciding.
      • I also found it striking that 80% of Mayo and trial patients getting LALs selected monovision/blended vision (5:10 in the video). I suppose the LAL patients are a biased sample (probably?) but that's still a pretty big percentage, which suggests that LAL is particularly effective for monovision patients, and also that a lot of patients who try monovision will like it.
    • RonAKA
      RonAKA phil09

      Edited

      Yes, there was also a disproportionally high number of patients that had prior refractive surgery.

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      The point in the video that shocked me the most was the question of whether or not you could leave the IOL in the eye if it was inadvertently inserted backward (from front to back). The answer was a hard no as the UV resistant side would be at the front and would block the UV needed to adjust the lens. What shocked me was that it was implied it may be common practice to leave a standard IOL as is, if it was installed backward! Later I saw a comment from another surgeon who described it as the "dreaded S shape". I guess the haptics on IOLs have some kind of convention that they look like a Z not an S when you view them from the front of the eye. S means backwards!

    • phil09
      phil09 RonAKA

      Posted

      Wow, that is shocking. Presumably only rookie cataract surgeons make that error. Reckless rookies.

      Reminds me of surgeons who write on patient body parts, things like "Not this arm!!". Maybe IOLs need a peel-off label saying "This end up."

    • RonAKA
      RonAKA phil09

      Posted

      You can find a video on line showing how it happens and how it is fixed. Looks to me like they have to poke a second hole in the capsule flip the lens. The video narrator says the S shape stands for stupid mistake!

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      My wife has had both hips replaced and both times she was asked to use a felt marker to write Yes on one hip and No on the other hip.

    • phil09
      phil09 RonAKA

      Edited

      "I think the value of this data is in what people choose when they have options to try out for real. The preference is personal of course, and I see one patient opted for -2.0 D. I think looking at this is helpful for those picking a target for monovision with plain monofocals. We can benefit from the experience of those who have paid $10K plus to use the LAL!"

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      I agree with all of this, but the data should be interpreted carefully. Just before the 21:00 mark, Dr. Mahr says LAL blended vision patients "oftentimes" end up selecting myopia of only 0.25 D or 0.50 D because of the lens' EDOF properties. So, while the observed average myopia for LAL was about -1.3 D across two FDA data series, there appears to be wide dispersion about the mean - significant numbers of patients prefer -0.5 D, and many others must have chosen -2.0 D or so.

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      Furthermore, if the LAL average is -1.3 D, presumably other monofocal lenses without EDOF properties would average higher myopia for monovision patients.

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      One other data point - one cataract surgeon who is prominent on the interwebs but our moderator seems to want to remain nameless, talks about targeting -0.75 D or -1.00 D on blended vision for LAL patients. This relatively low level of myopia is also attributed to the LAL's EDOF.

    • RonAKA
      RonAKA phil09

      Edited

      This issue I have with the LAL EDOF properties is that it is an undocumented mysterious quality. I noticed that the Mayo surgeon was very cautious in answering the question about it. He said something like "We are still learning". Seems to me if RxSight wants to make the EDOF claim they should be getting it approved by the FDA with a clinical trial.

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      I forget now what the graphs suggest, but it the lens works the way the anecdotal narrative claims, you would expect patients that started with lots of hyperopia and were corrected to low amounts of myopia would be the ones settling for a small amount of myopia because they got EDOF. Not sure that was the case, but the graphs did not include a lot of people. I also do not recall seeing people that got -1.50 backtracking to less.

    • phil09
      phil09 RonAKA

      Posted

      Yes, I would really like to know more about this as I come to a final decision on the lens I want for my myopic eye.

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      He-who-must-not-be-named implied that he starts both eyes at about plano, and simply adds -0.75 D or -1.00 D of myopia to the near eye. This is said to produce grade A near and intermediate vision from the myopic eye, complementing grade A intermediate and far vision from the distance eye.

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      This sounds very good, but I wonder whether I should want this undocumented EDOF effect. Maybe there is a downside? I also wonder what other undocumented - or unintended - effects may occur that could be more problematic. Most of the information I see indicates good outcomes from LAL, but I would feel better with more transparency.

    • julie66167
      julie66167 phil09

      Posted

      I wish I knew who you were referring to. Who would not want:

      "He-who-must-not-be-named implied that he starts both eyes at about plano, and simply adds -0.75 D or -1.00 D of myopia to the near eye. This is said to produce grade A near and intermediate vision from the myopic eye, complementing grade A intermediate and far vision from the distance eye."

    • RonAKA
      RonAKA phil09

      Edited

      As best as I can determine they are achieving an increase in depth of focus with spherical aberration. It works, but the price is some decrease in visual acuity. The enVista does this, and they probably make a good tradeoff in depth of focus and visual acuity. What would worry me about the LAL is that the increase seems to be a side effect of the UV adjustment process and not totally controllable.

    • phil09
      phil09 julie66167

      Posted

      There is a video entitled "How to select the BEST LENS IMPLANT for Premium Lens Replacement or Cataract surgery in 2023".

      Yes, it certainly sounds good, doesn't it?

    • julie66167
      julie66167 RonAKA

      Posted

      Is there an EDOF rating on the enVista? If I remember, the Eyhance is .3.0D?

    • RonAKA
      RonAKA julie66167

      Posted

      B+L publishes a useful graph showing the depth of focus for a few lenses. It shows the enVista at about 1.1 D. I would estimate the Eyhance at about 1.0 D. This is based on J&J's published data showing the differential between the Tecnis 1 and Eyhance. I have added my estimate of the Eyhance and added it to the graph. I will post it in the next post as it will get delayed until tomorrow in moderation.

    • RonAKA
      RonAKA julie66167

      Edited

      Here is the graph of depth of focus for various lenses as published by B+L. I have added the Eyhance as a red dot on the graph based on the published differential between it and the Tecnis 1 lens. The Eyhance fall a little short of the enVista. The AcrySof is about 0.8 D, and the Clareon I would expect to be the same as it uses the same amount of negative spherical aberration correction.

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      image

    • julie66167
      julie66167 RonAKA

      Posted

      RonAKA, I am sorry there is so much I don't understand.

      How do you convert microns to diopters?

      .

      Perhaps an IOL that comes with .375D EDoF - should not concern me? If "enVista at about 1.1 D. I would estimate the Eyhance at about 1.0 D." I realize this is an estimate. Does the Vivity have 1.5D?

    • RonAKA
      RonAKA julie66167

      Posted

      This is a bit of a busy graph. The vertical axis is the visual acuity. The horizontal is the depth of focus or depth of field. The points on the graph are different amounts of spherical aberration in micro meters. The more positive spherical aberration there is the more depth of focus you get, but at a small cost in visual acuity.

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      The Vivity has about 0.6 D more depth of focus than the AcrySof or Clareon. That would put it at about 1.4 D on this scale. The Vivity is using more than just spherical aberration to get the extra depth of focus, so does not fit on this curve which is mathematically derived based on aberration only.

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      The depth of focus is kind of a complicated number. Sometimes it include the distance on both sides of the peak vision point, and sometimes it does not. I believe these numbers are on the near side of full distance only. It also includes some assumption about what is an acceptable level of vision. 20/32 is often used for that.

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