Similar target versus result difference for both eyes after IOL?

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I have now had one IOL implanted (vitrectomy and IOL surgery) and am considering adjusting the lens target for the other eye based on the first result. I was aiming ideally for around -1.25D to -1.50D for one eye and -1.75D to 2.00D for the other using monofocal IOLs  after deciding against multifocal/EDOF etc.

The first eye had a target of -1.39D and the result is -1.00D (astigmatism reduced from -0.50D to -0.25D ).

My surgeon says it's likely the other eye will have a similar offset, and suggests allowing for an expected error of 0.4D, or half that if being more cautious.

So I am curious what people here have experienced with target versus result differences across both eyes?

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  • Posted

    Hi pg128, You and I are so similar: I had one eye done almost a month ago with monofocal, targeting -1.00D and got -1.00D at least initially. I suspect I have gotten a little more myopic, toward -1.25D, during this past month of healing. I should know in two days when I see my surgeon. I'll will have another eye done either next week or the week after, targeting 0.75D more myopic(-1.75 or -2.00D) than the eye already done. I'm also curious about if the offset will be similar between the two eyes.

    My surgeon also mentioned before surgery to expect 0.5D of error in either direction. I certainly hope it wouldn't go stray that far. She uses ORA to aid the determination of lens power. I'm not sure if it is important but she highly recommends it.

    How do you like the result of -1.00D? Now that's done, what will you target for your second eye?

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    • Posted

      I don't like the -1.00D result, so it looks like laser or piggy back lens down the line for me. I wish they did 0.25D IOL increments for more lenses as that would have given me a better choice and result. 

      I was hoping for results that fit very specific use cases (as my natural lenses did) for my work rather than the common -1.00D/-2.00D to provide reasonable correction-less/emergency vision.  

      My surgeon didn't seem overly worried with IOL result accuracy but I think he is mostly concerned with fixing the core vitreo-retinal issues which is understandable. In my case I had complications with my vitrectomy which could have been serious but appear to have resolved fortunately - I know some people who had the same surgery and weren't so lucky.

      We just need some more input of similarity of results as its hard information to come by.

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    • Posted

      It is interesting to hear your lens power preference. I actually wish my first eye to be less myopic than -1.25D, something like -0.75D. The reason is -1.25D is too myopic to watch TV well from 10ft out, as well as to drive without glasses. Everyone's vision preference is different. 

      I'll be seeing my surgeon in a few hours. I'll ask her if there is a similar offset tendency between two eyes. I re-read your earlier post and that prompted me to modify my second eye target toward less myopic, from -1.75D to -1.50D. I got the sense that more myopic second eye does not improve the overall near vision a whole lot, but only to result in a bigger monovision. I hope I'm right.  

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    • Posted

      I've been testing with contacts to simulate results as best as I can given my left natural lens still has around 0.5D accommodation (I've got 12 multifocal and 8 monofocal types of contacts in stock)

      The difference testing with lenses over the IOL versus real lens is significant due to the remaining accommodation.  Today I've been trying -2.00D using +1.0D over my monofocal IOL and I don't like it.  The distance is too blurry and the very narrow range of focus (around 48cm) is not worth it.

      A similar test using a +0.50D lens over my -1.50 natural lens to give -2.00D seems okay due to that little bit of accommodation.

      I am comfortable in choosing the lens, its just this random +/- 0.5D result that is the problem.  Ideally I want the other eye around -1.5D to -1.75D as per your thoughts, but hitting that range is the problem!

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    • Posted

      I too am curious about .5D accommodation.   I thought the eye’s natural accommodation had to do with age and natural break down of the ciliary muscle and accommodative system.  With slowing production of collagen, the elasticity in the lens inside of the eye, the lens loses  its ability to flex.  

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    • Posted

      Yes the natural lenses accommodation is lost for the reasons you mention as well as thickening of the lens apparently.  

      It appears I've been on the lower range of accommodation all my life (needed readers from mid 30s) and based on my tests I am down to about 0.5D in my un-operated eye as per my other post.

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    • Posted

      Lol you must be driving yourself crazy trying to work out a good target to aim for!   And yes not an exact science reaching the desired target.

      Do you have a surgeon willing to dialogue about all this.  Mine discussed my desired outcome:preferences but didn’t get into numbers / but neither did I ask.  They are so busy here.  Only 2 days a week to see patients- other 3 spent doing surgeries.  I wanted a second discussion after I mulled over first one and it took a month to see him and pushed my surgeries out 2 months. But that is par for the course in Canada.

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    • Posted

      My surgeon is mostly concerned with vitrectomy result which as is my case he did that with the lens and posterior capsule cutting. I've had a very good, but not perfect result with vitrectomy (possibly need another tidy up vitrectomy later in the year).

      He said he decides targets for most patients after some basic questions, but does discuss other options when asked. Understandably with someone like me he's let me choose but what I've gone with isn't much different from one of his favourites of targeting similar to current prescription for older patients with a reasonable amount of presbyopia and who are comfortable with their current prescription. 

      In the UK it also takes time even with the most expensive private hospitals, and in my case I needed an experienced vitreo-retinal specialist. Fortunately I am having my two surgeries only two months apart as having one eye with a mass of floaters and one without is very odd.

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    • Posted

      Cataract (or RLE) surgery is not that precise as you have seen, your 0.25D range for your target is too narrow for current practices.  The IOLs come in 0.5D steps and then there is the variability of how the cornea heals that is impossible to predict and varies with each individual.  Thats why getting within 0.5D of the target is considered "good" as well as if the residual astigmatism is 0.5D or less.

      If you require getting closer than that to the target, you would probably require LASIK or PRK "tweaking" after the cornea heals in a few months.  Some of the clinics offer a premium deal that includes these laser "tweaks" in the total cost.

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    • Posted

      I appreciate my ideal target is too narrow, I am just trying to reduce the chance of needing laser or piggyback lens (which also come in 0.5D steps according to my surgeon so about 0.35D in normal prescription terms).

      I've have carefully navigated my way through three years of treatments for several eye conditions, then for floaters and now vitrectomy and IOLs so I am getting a bit tired of doing more to the eyes.  At least I have made a big step back to good vision which looked unlikely at some points. Hopefully the other eye goes as well and in the grand scheme of things the exact prescription is not that important.

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    • Posted

      How did you get on with the surgeon, and possibly second surgery by now?

      I am about to see my surgeon for the difficult choice between -1.99D target or -1.64D (ideally I want -1.50D to -1.75D in that eye).  The difficulty being how, or if, to apply a correction given the first eye ended up -1.0D instead of the -1.39D target. I actually think its more -1.1D given the focus range even allowing for the astigmatism

      Since my earlier posts here I've found a couple more factors that add to the difficulty in predication:

      1) IOLs have quite a margin for manufacturing error. I believe the max is +/- 0.25D and even some lenses made in 0.25D increments still quote +/- 0.10D.

       

      2) Age also affects the calculations and one study I found showed the younger the patient the greater the error which was attributed to the formulas being based on the normal older age group

      With the above and differences in how the surgeon implants and the eye heals leads me to believe any error less than +/- 0.50D could consist mostly of these random factors and so not as useful for adjusting the other eye's calculation. That seems reflected in various information I found which suggests allowing 50% at most of the first error in adjusting the second and warns about allowing for +/-0.5 or less errors.

      I think I just need to accept I will need some laser correction to get the tight tolerances I need for my intermediate to near range mini-monovision to work well. It seemed a good plan as it was how my natural lenses were, but not so easy to achieve!

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    • Posted

      Sorry just saw your post. My second eye(left) was operated 10days ago (1/22, Monday). Two days post-op checkup showed it in-between -1.50 and -1.75, exactly as was targeted. If my the healing of my right eye is any indication, I expect it to shift to a little more myopic after healing(-1.75).

      Prior to surgery, my prescription was -6.00 right and -6.50 left. They put the same 13.0D monofocal lense in both eyes. So it was almost like clockwork, my eyes were corrected to -1.25 and -1.75 after surgery with the same spacing between two eyes before and after. Considering how you have listed so many factors, my case seems too easy....

      Now that I'm almost done, I'm quite happy with excellent intermediate vision and no artifacts, I have yet to receive the distance glasses which should correct my vision to -0.75/plano. Again, I wish my right eye is less myopic than -1.25. Either -1.00 or -0.75 will do so that I can watch TV and drive without glasses. I know you wish to replicate your prior vision but consider this: someone in this forum would be elated to be in your shoe...lol 

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    • Posted

      Thanks for the update Robert. 

      I am just about to have my second eye done and the first now fluctuates between -0.75D and -1.00D so 0.40D to 0.65D off the -1.40D target.   I am currently still deciding on the other lens which has target options of -1.65D or -2.00D and given the error on the first I am leaning towards -2D which the hope it will end up a little less myopic as the other eye did.

      However I did have a leak from a vitrectomy port in the first eye which meant delayed healing of the eye surface after it ballooned and required padding for some time. I am not sure if that could affect IOL position or healing.

      I've had significant starbursts since the first surgery with house lights as well as car/street lights, and now the eye surface has healed I have (or can finally see) positive dysphotopsia and the feeling there's a darker area in the periphery which makes vision feel more narrow than before. This last issue could be lens related but I did have some precautionary freezing of the retina so who knows.

      I knew the surgery to reduce/fix my very serious floaters would have downsides (and that is vastly better, not 100% but greatly helps reading) but the lens issues are a bit more than I expected given I went for a monofocal lens (Tecnis).

      I am just hoping the surgery for the second eye is a little less eventful!

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    • Posted

      Yeah, my surgeon says this more than once during post-op checkup: I'm concerned about retina problems and infection more than anything else(prior to surgery, I have mild horseshoe tear and dry eye problems). The diopter inaccuracies can be easily remedied by wearing either glasses or contact lens, whereas complications are a lot more troublesome.

      Wish your second eye surgery goes smoothly with zero complications!

       

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    • Posted

      Forgot to ask, did your surgeon comment on how likely your second eye was to shift off target the same as the first?    In your case it appears very little error so maybe just the tiny random variations (I've read less than 0.5D is not worth adjusting for).

      My surgeon said options are to allow for the same error, half the error, of none. However he wouldn't make a suggestion as to which approach gives the best chance.  When pushed he commented I have overly high expectations (which isn't the case) I just want to make a well considered choice.

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    • Posted

      My surgeon mentions a couple of times the resultant diopter can vary by as much as 0.5D in either direction. They are smart to say that to cover their asses. She did say that the vision shift during the period of healing could follow the same pattern. In my case, my right eye shifted a little more myopic during the weeks after surgery. She expects my left eye to do the same.
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    • Posted

      pg128, just curious, what do you think your vision would be like in the following scenarios: -1.25/-1.25, -1.25/-1.75, and -1.25/-2.25? I know you are targeting -1.25/-1.75. If you have to choose between -1.25/-1.25 and -1.25/-2.25, which one would you choose? 
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    • Posted

      It'll be no surprise that I've tried to simulate most of those, especially post the first surgery. The challenge simulating now is having one eye clear of moving floaters and grainy vitreous and the other still grey and full of bits. I can tell my brain is favouring the good eye whenever possible. 

      Anyway, best as I can answer (I have -0.5D astigmatism which would improve close vision even more):

      -1.25/-1.25 comfortable for computer screen but the lack of near means grabbing readers too much.

      -1.25/-1.75 Ideal for me and in effect what I had before surgery allowing for the tiny amount of lens adjustment left and my astigmatism.  Works for computer screens, tablet and phone distance and not too much difference in power so reasonable depth perception etc. Readers only needed for really close.

      -1.25/-2.25 Difference getting towards limit for comfortable vision (I've never tried a long term -1D mono-vision test, just a day or two).  Should provide near seamless vision over close to intermediate though, at a 1.5D difference a gap starts to be noticeable between the two lenses optimum points.

      There are so many scenarios with daily activities, and I also used to wear mutli-focal contacts which I've been trying but as before they're getting harder work with age and dryer eyes. I also note all contacts add a ring around vision over my IOL which didn't happen before.

      As to the -1.25/-1.25 and -1.25/-2.25 question. This is close to one scenario I've been pondering instead of sleeping recently with just three days to go before surgery (I am quite stressed about the vitrectomy part of the surgery so my decision making is not what it usually is!).  If I choose a -2D target worse case scenario is it moves more myopic leaving me -1.0D/-2.25D or more and its the 1.25D difference that concerns me.

      But my choice right now from those two would probably be -1.25/-2.25

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    • Posted

      To me, all three are really not all that much different. Each option gains in some areas but loses in others. My current vision is -1.25/-1.63. It is excellent within the distance of 15" to 4-5 ft and in depth of field due to small monovision. However, on the distance side of the vision, TV viewing and driving are not good, and on the near side, newspaper reading is also not good especially in low light because I have to read from 15" out. With that said, I agree with you that I would prefer -1.25/-2.25 over -1.25/-1.25, though only slightly.

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    • Posted

      Yes I agree the differences are small, my preference is probably just because that's familiar.  The problem is without accommodation using monofocals we really need three prescriptions. We can choose to aim for one being excellent (and hope we get lucky obtaining it) or settle on one very poor and two little compromised due to monovision. 

      With hindsight I think close/intermediate mini monovisions of 0.5D to 0.75D are a risky option as its easy for one or both ends to move too far as happened with me.  Intermediate to distance mini monovisions are less risky due to the greater range of focus per dioptre.

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    • Posted

      Just wondering - did you try any monovision close/intermediate tests before deciding?  

      I did but a contact lens test but its hard to get a feel over a real lens or mix of IOL/real. Also not easy spending enough time testing given glasses/normal contacts are needed for distance activities/work.

      For me 1.25D seemed too much, 1.0D was easier but still felt less natural (not a long term test though) and finally 0.75D seemed a good compromise and comfortable almost straight off.

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    • Posted

      I have a 40-day tryout with contact lens after my first eye was done. I tried both -1.25/plano and -1.25/-1.75. The tryout was not ideal because my second eye had pretty bad cataract. Nevertheless, it was enough for me to choose -1.25/-1.75 over -1.25/plano.

      Now I have -1.25/-1.63, I have no problem with mono vision whatsoever. My surgeon advises me to get glasses for plano/-1.63 because herself is plano/-1.75. I tried that and didn't like it. It will take a while to get used to that amount of mono vision. I'm just not convinced I will like it "even after my surgeon "guarantee that I will eventually get used to it". I have been wearing glasses for plano/plano during this past ten days. It is easier to get used to it even though I know this is not a long term solution. I just received the glasses for plano/-0.63. We'll see how I like it. Stay tuned.

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