The Pros and Cons of Mini Monovision
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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:
- 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.
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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.
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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.
11 likes, 250 replies
soks RonAKA
Edited
Attached is my iol master using barrett at wills eye. i am refracting exactly like you in the right eye for alcon lenses and i consider that lucky if you are choosing alcon because -0.45 is negligible and with vivity gives you quite an advantage.
RonAKA soks
Posted
I believe that post was intended for David. In any case I noticed that they RE predictions landed in a bit of an awkward spot. -0.10 is a bit too close to plano to risk, while the -0.45 is a bit much for a distance eye.
soks RonAKA
Posted
i think it is a good spot to be in because the decision is made for you to go with -0.45 and i experience the vision to be better than Symfony at -0.19.
RonAKA soks
Posted
Well it should help a little with the near vision end of a MF lens. My distance eye vision has drifted a little and now I am about -0.375 D SE which is close to this point. I started at -0.25 D which I liked a little better.
David970 RonAKA
Posted
Ron, how do you measure with such accuracy? Autorefractor?
Before the cataract, I went to the same doctor 2 times a year and each time I received + -0.5D on the same device, although I wore glasses for more than 20 years -6D. I read in the comments on youtube that someone bought a set of lenses and measured their own vision. This is more accurate than the doctor's, because you yourself are not in a hurry and you can repeat as much as you want for accuracy.
Thanks for the Vivity defocus curve.
Is there no such curve for Vivity -0.5D? Or do you think -0.5 is the wrong option? It's just that most of the medical studies of micromonovision for Viviti are just done with a shift of -0.5D.
RonAKA David970
Edited
The key is the "about" preface to the number. The number implies more accuracy than there really is, and number is an artifact of calculating the spherical equivalent. In this case it is 0.0 sphere plus 50% of -0.75 D cylinder from a phoropter measurement. A phoropter is a +/- 0.25 D measurement so that is the underlying accuracy. What I notice however is that sometimes the cylinder and sphere kind of flip. On one visit the sphere may be a 0.25 D step more, and cylinder 0.25 D less. I think depending on the day I must choose cylinder over sphere and the next time vice versa. I would not trust an autorefractor measurement, and I think the phoropter is the gold standard.
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Those curves were one I derived from the Vivity Package Insert document. I just plotted the original curves as close as I could from their graphs, and then I added in the various offsets, and let the spreadsheet replot them. Those offsets were just what I was thinking at the time for myself. I later switched the monofocal from a 1.25 offset to a 1.50. You could get -0.5 D for an offset on the Vivity by just sliding the curve 0.25 D less than the -0.75 D curve. The curves should be identical, with just the offset changing.
joseph54594 RonAKA
Edited
@RonAKA Sorry,,if this is repetative. I check in for cararact surgery in 5 hours from now with a monofocal lens for distance.
You have excellent vision from 8" and with most night driving at -.25 distance and -1.40 for near vision, I believe My surgeon has deferred to my Optometrist, who reccomends .50 for distance and 2.5 for near. He does not implant IOLs, so I am not sure if that matters. He came up with that because I want near vision at 13" He said I may need glasses for driving. The distance of 2 D is a lot and I have not been tested for tolerance. I can make the close decision later, but, today, I hate to tell them .25 for distance if that will mean trying to set up a close setting that isn't as good and asking for mini monovision, but I do not know if I can go back to .25 once it is set. My optometrist did use a calculation, but maybe for contacts, so I am wondering if the D settings are different for IOL?
RonAKA joseph54594
Posted
I suspect he is talking about the same D (diopters). It is based on what is required to correct your vision to plano. If you go with -0.5 D for the distance eye it gives you more margin against ending up positive or far sighted, but if they hit it, then you will lose a bit of distance vision, but may still have 20/20 or close. If they miss by going more negative such as to -0.75 D, then the loss of distance vision will be more significant.
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On the other close eye, yes for sure targeting -2.5 D is going to give you better near vision. However it may have some issues. You may end up with a section of intermediate vision where you don't see that well. Also it may be hard to adapt to with a larger differential between the eyes. The standard recommendation is to keep the differential to 1.5 D between the eyes. So what I would suggest after your distance eye heals (6 weeks) then get an eye exam to find out where you ended up. If you land at -0.5 D then you could target -2.0 D for the near eye. If you land at -0.25 then you could target -1.75 in the near eye.
joseph54594 RonAKA
Edited
Thank you! The day after my right eye was done, I went in and was at 20/25 and they said it would get better as the eye heals. I have not tested it driving since getting home, but distance I'd great and intermediate is, too, even though it is a mono focal lens. They used the Softec HD lens and so far, so good. I have tremendous contrast and even came home and saw dirty sinks that I thought were clean! My car looked new because I saw the shine! Maybe, I will get the left eye done with less than 2.5D since I am already seeing my cell phone at 13", but not clearly, but it feels like I don't need a huge correction to achieve that.
RonAKA joseph54594
Edited
Once the eye heals and is stable you can estimate home much more myopia you need to read by using reading glasses. So for example if you end up at -0.25 D and find +1.25 D readers are good enough, then you would target the total of -1.50 D for the other eye.
RebDovid RonAKA
Posted
A 2 D differential is quite large and, therefore, quite risky unless you have tried it successfully with contact lenses. If by now, it's too late to delay or change your distance target of -0.25 D, then I suggest delaying your second eye until after your first eye settles, you and your surgeon know the actual refraction, and you trial monovision with appropriate contact lenses in the second eye. Whatever differential you find you can tolerate, I would ask your surgeon to try to undershoot by some safety margin.
judith93585 RonAKA
Edited
Hi RonAKA, Could you clarify my confusion about toric lOLs? I had originally understood that toric IOLs were generally most effective for distance, not so much for near. That made me question any suggestion that I get toric for IOLs set for near. Then I noticed your statement below that suggests that toric would have improved your vision in your near eye, could you clarify for me?
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.
RonAKA judith93585
Edited
Astigmatism is like having a football shaped eye rather than a round one like a basketball. The shape of the eye affects vision at all distances. However, one may notice it more at distance than close up. The astigmatism I have in my near eye is called irregular as it is not symmetrical with more on one side than the other. In any case I get a drop shadow on letters which makes them a little harder to read. I have 0.75 D astigmatism in both eyes based on my last test, but I only notice it in my near eye. That may be the impact of the irregular part.
judith93585 RonAKA
Edited
Thank you! I remember that someone in the group advised me to ask about my anticipated residual astigmatism once my natural lenses have been removed, since astigmatism can often decrease after the natural lenses (cataracts) have been removed. I thought that meant that I might not need toric lenses after all. It sounds like that was a misunderstanding?
I find myself still confused regarding toric lenses... My first understanding was that toric lenses would help anyone with astigmatism over 1 D? Then I read that toric lenses only help with IOLs set for distance. Then I think I read that toric lenses can correct near sightedness or far sightedness without other measures, but I assume that is not correct... Can you clarify these points? Many thanks!
RonAKA judith93585
Edited
The lenses vary slightly on the minimum amount of cylinder they can correct. Some lenses are 0.75 D and others are 1.0 D. If you have astigmatism it will affect vision at all distances. It would not make sense to correct astigmatism only and not also correct for sphere to where you want to go to.