The Pros and Cons of Mini Monovision
Posted , 34 users are following.
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?
.
Cons:
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
.
Pros:
- 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.
- 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.
- 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.
- 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.
- 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).
- 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.
.
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.
.
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.
.
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.
.
I hope that helps some, for those who are considering this Best Kept Secret option for IOLs.
11 likes, 250 replies
ka76787 RonAKA
Posted
How much astigmatism do you have in your near eye? I'm curious if 0.85D of astigmatism should be corrected in a near eye. I had one surgeon say it should be corrected and another say the astigmatism would be beneficial for near vision/reading text so it should be left alone. Planning to target about -1.5D of myopia.
RonAKA ka76787
Posted
I have -1.25 D sphere and -0.75 D cylinder in my near eye for a spherical equivalent of -1.625. That is right on the borderline as to what they correct or not correct. AcySsof make a low cylinder -1.0 D toric that I probably should have used. If I had done that I would have had to increase the sphere to maintain my reading. Astigmatism has about a 50% weight in increasing reading, but they makes letters less crisp. It is a bit of a tradeoff. It is better to get near with pure sphere if it can be done.
.
I don't think the lenses you are looking at are available in toric versions? You would have to use LRI which my surgeon said is not that predictable, or Lasik to reduce the astigmatism. If you plan to use Lasik post surgery it would be best to SE for higher myopia than 1.5 D so you will maintain about 1.5 D SE after Lasik.
JDvision RonAKA
Edited
I would just like to add a simple way to think about mini-monovision for cataract surgery, having experienced it now for a bit - ability to pick two focal lengths (near and intermediate, or far and intermediate) to see uncorrected sharply vs one (near, intermediate, or far) post cataract surgery without mini-monovision.
When you get cataract surgery, your natural lenses may still have some natural accommodation left to refocus at different focal lengths, depending on your age and degree of presbyopia. Cataract replacement intraocular lenses (IOLs) generally have no accommodation at all, so you immediately switch from whatever level of presbyopia you had to maximal presbyopia, meaning monofocal IOLs will result in sharp vision at only one distance (near, intermediate, or far), which would generally require corrective lenses for the other two distances, possibly except in very bright light when your pupils are very small.
Without mini-monovision, assuming you pick monofocal or toric IOLs or otherwise treat any corneal astigmatism, you can pick one distance to be sharp uncorrected: near, intermediate, or far, with the rest requiring corrective lenses.
With mini-monovision and the same type of IOLs, you can pick two distances to be sharp, one for each eye - either far and intermediate, or near and intermediate. If you tolerate mini-monovison well (something you should test before committing to mini-monovision IOLs), your brain will integrate the two images, giving you near seamless sharp uncorrected vision at both distances, and depending on light level/pupil dilation and other individual factors, potentially decent vision at the third distance.
Picking near and far for the two eyes is not recommended as that is full monovision, and causes too many issues including difficulty for the brain to integrate images.
RonAKA JDvision
Edited
I look at it a little differently. I find the terms of near, intermediate, and far, quite misleading, along with the statement that monofocal lenses can only provide clear vision at one distance. The reality is that a monofocal can provide good vision over quite a wide range of distances. A standard monofocal targeted to 0.0 D or plano can provide good vision from the moon all the way down to 2-3 feet. That is a very wide range of vision, not a single distance. Yes, as one targets the lens to closer and closer distances the range of vision in distance is reduced, but it is still far from a single distance. A lens targeted to -1.5 D can result in good vision from 1 foot to 6 feet or so depending on the person.
.
From this my observation is that it is quite possible to target near and far with mini-monovision. There is no need to decide between intermediate/far or intermediate/near. When you target near and far, the intermediate range is covered by both the near eye and far eye. They overlap (in the 2 to 6 foot range) and provide binocular vision and good depth perception in the "intermediate" range. And the contribution from each eye are additive and result in better vision in that range.
.
Now, this said if one defines "near" as the vision that someone that is very myopic (-3.0 to -5.0+) gets when they take their glasses off, then no, that cannot be achieved with mini-monovision. Those people have super near vision that can only be achieved with reading glasses in addition to mini-monovision. And, even those that go with a multi-focal lens like the PanOptix are not going to get that super near vision either, and will need reading glasses too.
.
I find it unfortunate that cataract patients that have their first consult with the surgeon can come away with the idea that a monofocal lens only lets them see at one distance. Nothing could be further from the reality. And, almost nobody takes the next step in looking at the defocus curve for the monofocal so they can see the reality.
JDvision RonAKA
Edited
Here is the problem. It does depend a lot on the person. Defocus curves vary by person, so it is a mistake to go into cataract surgery counting on that when it is not assured. Better to be pleasantly surprised with better than expected vision than to be sorely disappointed with worse vision than expected (lookup loss aversion bias to understand why). -1.5D is 24" focal length, I believe and the actual defocus curve experienced by individuals depends on their natural pupil size/dilation characteristics, light level, and I suspect (haven't found evidence of this one, so this one is just a guess) eye geometry. Point being - how far off from 24" you can see sharply with -1.5D (for instance) depends on individual characteristics, and may not be fully predictable in advance.
As a case in point, I followed your advice of targeting max of 1.5D anisometropia and I'm happy with the result - happy with your advice. I have great uncorrected distance (even at night) and intermediate vision, and functional uncorrected near vision (I can do casual reading, restaurant, grocery store, etc, without reading glasses). I get great near vision with reading glasses. And no, I don't mean myopic hyper-near. But, I did not get as good results as you describe. And as you recently found out, neither did you. You said in the initial post:
But recently, you found out that was not the case, at least for smaller print menus.
I have locked in RxSight LAL lenses in both eyes (in effect toric to correct corneal astigmatism, but otherwise monofocal) near optimal mini-monovision with -0.125D and -1.625D SE (due to residual negligible 0.25D astigmatism in both eyes which may even add a bit of DoF as you pointed out), and in very bright light, I can read down to 14" clearly, or in normal light down to 16". 12" is blurry even in very bright light. Despite your claim to the contrary, I cannot read with my near plano (-0.125D SE) eye at even 3' without reading glasses - not even close (well corrected with reading glasses). That, in fact, is the reason I went with mini-monovision, to compensate for my disappointment with the near vision in my distance eye. But in all but the brightest light, I still prefer reading glasses for extended reading sessions to avoid eye strain, because while I can read, my eye muscles still try to accommodate to further improve clarity, even though the IOLs have no accommodation. In effect, I have mild residual presbyopia, which is 100% correctable to extremely sharp with reading glasses, so not due to other eye issues.
I should have clarified what I meant by near, intermediate, and far. I mean:
near: handheld reading, such as a book or a phone. 14" is the official distance used in a Rosembaum reading eye chart, but I'd say anywhere from 12"-18", depending on individual arm length (needs to be less, or at least no greater than arm length).
intermediate: reasonable desktop computer screen distances
far: TV or driving
I used the characterizations I did to say count on two of the three distances with mini-monovision or only one without mini-monovision using monofocal lenses, because everyone without other medical eye issues interfering should be able to achieve that. Getting the third distance range from mini-monovision is a bonus that some get, but it is not something to be reliably counted on, or many people will be quite upset. I again refer to loss aversion bias for why it is important to characterize having sharp vision in all three ranges as lucky, rather than expected.
JDvision
Edited
Above was supposed to read:
The frustratingly short edit timeout on this website didn't allow me to correct it in the original post.
RonAKA JDvision
Posted
A few thoughts:
.
But, this all said, there are no hard and fast rules. With a cooperative surgeon we get to do what we like. Not everyone has the same priorities.
JDvision RonAKA
Edited
Ron, I agree with most of your last round of comments. Just a few points of clarification:
Above is why I say mini-monovision can (confidently) give a patient two of the three distance ranges, but getting all three is lucky.
RonAKA JDvision
Edited
Sorry, but I can't agree that one needs to target far and intermediate, or intermediate and near with mini-monovision. It is quite a reasonable expectation to have good vision at all three distances. Keep in mind that it is normal to target -0.25 D in the distance eye and still achieve 20/20 distance vision. This means that the near eye which should be done second can be targeted for as much as -1.75 D, while still respecting the limit of 1.50 D anisometropia.
.
I was at -0.25 D in my distance eye after surgery, and if it wasn't for some issues over irregular astigmatism and whether or not it could be corrected with a toric lens, I would have gotten a toric lens along with more myopic sphere. This would have improved my near vision from what it is now. And what I have now except for some unusual vision circumstances easily covers all three distance ranges. Even better was possible.
.
Being older with smaller pupils increases the degree of success with mini-monovision with covering all three distance ranges not at all unreasonable to expect. And, unfortunately we all age at the same rate, but the upside is that studies have shown that the ratio of favourable results with monovision also increases as we age, with the need for eyeglasses falling as well. See this article.
.
https://www.clinicsinsurgery.com/open-access/monovision-strategies-our-experience-and-approach-on-pseudophakic-monovision-3455.pdf
.
Sorry for being sticky on this but I think mini-monovision with careful target planning can deliver just as wide a range of focus, or even more than a multifocal lens like the PanOptix. And for sure it delivers a much wider range than an EDOF lens targeted to plano.
JDvision RonAKA
Posted
Ron, thanks for the study link. Your (their) point about pupil dilation shrinking with age is an important addition to the discussion.
I also am not arguing for multifocal or EDoF lenses (of which I have no experience and for which I was not a good candidate). I know both can cause issues uncorrectable with glasses where residual issues with mini-monovision are correctable with glasses.
But my position regarding focal range for mini-monovision is supported by the data in the study you referenced. Specifically:
So that means only about 1/2 the patients were no longer glasses dependent a year after surgery. Meaning 1/2 of them still were glasses dependent after 1 year. Same as I concluded from the study I quoted. You cannot count on good uncorrected vision at all three distance ranges, but you may be lucky enough to be in the half that get it right away. The great news from the study is that due to pupil dilation changes with age, glasses dependence is likely to improve substantially as patients age, with impressive reductions in glasses dependence at 5 and 10 years (at least for patients older than 60).
Note this isn't about your individual results or mine (my mini-monovision is tuned within 0.125D SE of where you recommend), but rather the odds of an average person having good uncorrected vision at all three distance ranges from tuned mini-monovision.
With mini-monovision, those odds are about 50% in the first year and (great news!) improve significantly over the next decade as pupil dilation shrinks with age (at least for patients older than 60, per the study).
Actually targeting near/reading with monovision so it was in focus for all (rather than 1/2 in the first year) patients with a range of pupil dilations would require -2.5D in the near eye, as that is a focal length of about 16", which is close to the 14" standard for reading (Rosenbaum chart standard), or -2.8D, which is 14". I am ignoring the defocus curves because they vary with pupil size, and I said for all patients with a range of pupil sizes. Neither you nor I would recommend that if the distance eye targets plano as it exceeds the 1.5D anisometropia limit for mini-monovison and starts causing issues due to the large difference between the eyes. Full monovision in that range is rarely used today.
I think you do a great service to patients to inform them of the little known benefits of mini-monovision (up to 1.5D anisometropia) for cataract surgery, but setting the expectation that they will see well at all distances is setting 1/2 of them up for disappointment as only about half will achieve that within a year of surgery. That is why I said it the way I did regarding the three distance ranges, and both studies provide evidence supporting that position for at least up to the first 5 years after surgery. With the additional study you referenced, I'd add that the odds of reducing or eliminating glasses dependence for the 3rd (not selected) range are high within 5-10 years for patients over 60.
jo61855 JDvision
Posted
"In this strategy, we implant a monofocal IOL in the dominant
eye and a diffractive multifocal IOL in the non dominant eye. With
this type of binocular vision, patients do not complain of discomfort,
and more than 85% are satisfied with their results. We have noticed
a relative decrease in stereopsis; however, the normal range was
maintained in 63% of patients. No serious complaints have been
reported after hybrid monovision [5]."
jo61855
Posted
Stereopsis is "the perception of depth produced by the reception in the brain of visual stimuli from both eyes in combination; binocular vision." "Stereopsis is the visual ability to see your surroundings in three dimensions (3D), allowing a person to judge the distance between themselves and objects around them."
Lynda111 JDvision
Edited
This is another more recent article about mini-monovision.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9755282/
RonAKA JDvision
Posted
I remain unconvinced that one should not expect a full range of vision from properly implemented mini-monovision. Will it be perfect? No, of course not. Can it go a long way to make one eyeglasses independent most of the time? Sure it can as long as the targets are properly selected. Will OTC readers be needed for some difficult reading situations. Yes, for sure. Are prescription glasses needed for driving at night in the country where it is very dark. Yes, that would be a good practice.
.
I also do not think one can dismiss full monovision or at least more than min-monovision. Some do it and like it. In that article I posted, the average in the non minimal monovision section had -2.0 D in the near eye. They achieve very high eyeglass independence and satisfaction. However, if one is going that route, it would be more important to do a contact lens trial.
.
I think one needs to be flexible with a plan, rather than decide up front what is the best way to go. If one targets distance vision with the first eye and end up at the magic perfect -0.25 D, then it would be quite reasonable to target -1.75 D in the near eye, rather than -1.50 D. And, if one is unfortunate enough to get -0.5 D in the distance eye, then a decision has to be made. One could accept getting less than 20/20 but still driving legal distance vision and then go for -2.0 D in the near eye. Or, one could abandon ship and try for closer to plano in the second eye.
.
It is also worth considering what the worst outcome could be. If one does not get the full range of expected vision then eyeglasses are a good solution. If one chooses near or far in both eyes there is a 100% chance of needing glasses. Monovision give you a good chance of being eyeglasses free vs 100% chance of needing them.
JDvision RonAKA
Edited
Ron, I agree with most of what you said. Just need to comment on a couple things:
Both studies showed around or up to 50% of patients having post-surgical glasses dependence in the first year (which is likely to improve over 5-10 years, at least with ~2D anisometropia for patients over 60). And as you point out, in the study you provided, the average anisometropia was ~2D, which exceeds the 1.5D mini-monovision threshold, so glasses dependence likely would have been somewhat worse if they had limited to 1.5D (they now use lower anisometropia for small pupils - the study was for surgeries at least 10 years earlier).
Merriam Webster defines expect as:
So no, one should not expect a full range of vision, given 50/50 odds of glasses dependence after one year. Rather, one should aspirationally strive for it with flexible planning and adjusting along the way as necessary (as you say), and hope for it, but not expect it.
The way I navigated it was I asked for and managed to a target of glasses independence for far and intermediate, and as little glasses dependence as practical for near (without meaningfully compromising uncorrected night driving, eye fatigue, depth perception, and sensory fusion with increased DOF due to mini-monovision). When I was undergoing LAL adjustments in my near eye (distance eye was already locked in near plano), I tested night driving with the adjusted LAL and with a pair of reading glasses in addition over just that eye to have a good idea at what point the dysphotopsia effects would become a problem in binocular vision and stayed below that. I'm happy with the result but if I had gone into it expecting good uncorrected vision at all distances (from say 12" or 14" to infinity), I would have been disappointed and mad at whoever mis-set my expectations. To be clear, I have functional uncorrected vision at 16"-18" depending on lighting, which is fine for casual reading, but not for sustained reading without reading glasses.
JDvision Lynda111
Posted
Thanks Lynda. In the newer study you reference, they do appear to achieve more glasses independence with lower amounts of anisometropia. However, this appears to be specific to the IOL they're testing, which they claim can already handle two of the three ranges without anisometropia, so they add the third range with it. I don't know details about the lens, except that it sounds like an EDOF lens, but they're calling it a monofocal and claiming it doesn't have the dysphotopsia issues of EDOF lenses. I wonder if it is simply an unlabeled low EDOF lens.
RonAKA JDvision
Posted
The Eyhance is said to add about 0.25 D of extra depth of focus, which is in the noise range for eye refraction. There is no way it is close to the 0.5 D needed to call it an EDOF and J&J knows that.
julie66167 RonAKA
Posted
Have to ask - what is "noise range for eye refraction"?
RonAKA julie66167
Posted
I just mean that when eye vision is measured with a phoropter, which is considered the gold standard, the measurement steps are 0.25 D. It is a very small value in terms of eye refraction.
JDvision RonAKA
Posted
Thanks for the confirmation Ron. That is what I suspected: unlabeled low EDoF, but since I hadn't investigated Eyhance, I wasn't sure.