Monofocal iol set to plano

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Hello, I will have implanted monofocal iol soon but am very confused about it. Please could someone explain this to me? 

So, the lens can be adjusted to see only at once focus. What does it mean? What is a 'focus'? From 10 cm to 20 cm? Or from 10 cm to 1 meter? What is depth of field of this focus? 

I have one more question: usually, in healhy eyes, the closer we go to zero, the best is the sight. I heard that with monofocal one eye is set to, for example, -2 or -3. What does it mean?

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  • Posted

    The monofocal lens is choosen so that it has a best focus at the desired distance. If each eye is set to see the best at far distance, it corresponds to requiring a spherical correction of zero for each eye to see at far distance. This is the option used most often. If used, one will require glasses to read well at near (about 40 cm) or the intermediate distances (about 66 cm).

    As an option, if one eye is set for far distance, the other eye can be set for the best focus at about 100 cm. This will correspond to requring a prescription of -1.0 D for far distance for that eye. The 2 eyes together will then be able to see well from about 65 cm to far distance. One will still need reading glasses. There is some adjustment required from the brain to deal with different prescription for the 2 eyes (called monovision), but most people can adjust to it (it took me less than 5 minutes to adjust to a much larger difference in the 2 eyes when I tried monovision many years back with contact lenses. This will be my recommendation if you will like to use the monofocal lenses only.

    One can even have one eye set for far distance and the other one for reading (corresonding to about 40 cm and a prescription of -2.5D). I have that combination using a Symfony lens for distance and a monofocal lense for reading with  very good day time vision at all 3 distance ranges (but have the night vision issue associated with the Symfony lens). However, if one uses that combination with the monofocal lenses, the lack of good vision at the intermediate distances may be a problem.

    The depth of the field of focus depends on the amount of light. In good light, a lens set for far distance will provide reasonably good focus from about 200 cm and beyond, a lens set for 100 cm will provide a reasonably good focus from about 66 cm to 200 cm, and a lens set for 40 cm will provide a reasonably good focus from about 33 cm to 50 cm. All these numbers are based on having minimal amount of astigmatism in the eyes.

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    • Posted

      thank you very much indeed! My grandad has two near monofocal, he need glasses for watching tv but he goes around in the house without wearing them. how is that possible? the bluriness is not that strong? I'm myopic, so used to see dreadfully far away, already from 50-60 cm and beyond. I have also keratoconus and irregular astigmatism.

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    • Posted

      I think that that unless one is trying to read something or is interested in some detail, it is hard to know how good or bad the vision is. Thus, your granddad knows that he needs to wear glasses to see the TV well. So, he uses the glasses. Even though his intermediate vision is probably not good to read at 100 cm, for example, he can still move around fine even if the vision is not good at that distance.

      As an example. before my cataract surgery, when wearing my contact lenses with one eye set for far distance and the other one set for reading, my intermediate vision was fine for day-to-day activities and I never wore glasses. The only time I missed having good vision at the intermediate distances was at some unusual situations, such as trying to read captions from about 70 to 100 cm away next to paintings in a museum. So, it all depends on your life style as to how good a vision you need to have at the intermediate distances.

      My suggestion will be for you to either have the combination of far / intermediate or intermediate / near focus for the 2 eyes, depending on whether you would prefer to use glasses for reading or for driving / watching TV.

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    • Posted

      Thank you! Tell me something please that I really don't understand: what is the difference between wearing glasses for far away when you are myopic and still have your own natural lens and wearing distance glasses when you have monofocal for near vision?

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    • Posted

      The difference is not that much. The exact difference depends on how much natural focus adjustment is still left in your natural lens (even if you are myopic). The older a person is, the lesser the natural adjustment tends to be. The monofocal lens, which you will have after cataract surgery, will have no focus adjustment. Thus, there will be some loss of range in the distance over which you will be able to see clearly.
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    • Posted

      I have two more questions please:

      1) How is the level of bluriness for the not corrected distance by monofocal iols?

      2) If I have implanted monofocal for close, wearing glasses for distance, lets me to see close even with glasses on? Or I must put them down?

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    • Posted

      If you get both monofocal lenses for reading distance of about 40 cm, your uncorrected far distance vision will be rather blurry: probably about 6/30 in the metric system.

      Also, in that case, if you were wearing glasses to see at a distance, you will have to put them down to read unless the glasses were bifocal, trifocal, or varifocal.

      I really think that most people can adjust to small differences in the prescription power for the 2 eyes (i.e.micro-monovision). So, you should seriously consider one of the following 2 options:

      1. Have one eye set for far distance and the other eye set for the best focus at about 100 cm. This will correspond to requring a prescription of 0D and -1.0 D for far distance for the eyes. The 2 eyes together will then be able to see well from about 65 cm to far distance. One will still need reading glasses.

      2. Have one eye set for reading at 40 cm and the other eye set for the best focus at about 67 cm. This will correspond to requring a prescription of -2.5D and -1.5D for far distance for the eyes. The 2 eyes together will then be able to see well from about 35 cm to 100 cm. One will need glasses for distance (the uncorrected distance vision will be about 6/20 in the metric system).

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    • Posted

      What prescription would you suggest for piano playing/reading musical score?
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    • Posted

      That will depend on the distance range, which you feel that you will have to have to be able to read music while playing piano. If you can share that, then I may have a corresponding suggestion.
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    • Posted

      Seems like a distance of about 50 cm, which corresponds to a prescription of about -2.0 D.

      If you want to be able to do that without glasses, you can set both eyes to the best focus at that (or close to that) distance. However, my suggestion will be the option 2 above; viz, "Have one eye set for reading at 40 cm and the other eye set for the best focus at about 67 cm. This will correspond to requring a prescription of -2.5D and -1.5D for far distance for the eyes.The 2 eyes together will then be able to see well from about 35 cm to 100 cm."

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    • Posted

      I heard many people have troubles with monivision, with one eye far and the other near. Is that mini-monovision more natural? 

      I have one more question please: I have irregular astigmatism: is toric iol a good solution? I don't want to have aberrations, halos, glare and so on with a toric lens. How is about that?

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    • Posted

      The the mini-monovision which I am suggesting requires a difference of only 1D between the 2 eyes. That is very easy to adjust to.

      A Toric IOL can take care of regular astigmatism, but not irregular astigmatism. Thus, that will be of no benefit to you.

      If the irregular astigmatism is really bad, one can have LASIK enhancement done after the cataract surgery, but if you have been living with it all these years, that is probably not that bad.

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    • Posted

      Thank you very much, at201! Are you a doctor? You look very expert about those things smile Putting a toric iol with irregular astigmatism may not help at all about astigmatism or could even aggrave the situation with halos and other aberrations? 
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    • Posted

      I am not a medical doctor. Am just interested in being knowledgable in the areas which affect or have affected me.
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    • Posted

      Having an irregular astigmatism, does make the measurment of iol power problematic?

       

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    • Posted

      Usually, having a small amount of irregular astigmatism should not make it any harder to measure the IOL power. However, if your eyes are keratoconus, then depending on how bad it is, there is a potential for it making it harder for the doctor to determine the best power.

      As a side note, the determination of the IOL power can be off by about 0.5D even for people with no irregular astigmatism. So, it is good to have one eye done first and wait for 2-3 weeks for its vision to stabilize before selecting the best power for the second eye. This will be even more important in your case.

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