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What is a reasonable or safe target for a high myopic patient choosing monofocals?

Posted , 12 users are following.

sam36130
sam36130

I have two surgeons giving me very different targets for my L eye cataract surgery monofocals IOL. I like to set to see distance clear, and i am high myopic -11.5 in L eye while -10.5 in the other, what is a reasonable target that surgeons usually use ? one surgeon suggested -0.2, the second surgeon targets -1.0. Why a big difference? how accurate will these targets be after surgery (plus or minus 0.5 or more)?

i am at a lost here because i don't know which surgeon to trust since the targets are so different. The last thing i want is blurry at all distance with a monofocals!

thanks for any help you can provide.

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  • Guest
    Guest sam36130

    Posted

    none of the ophthalmologists i have seen told me that i need surgery. They only say if you want to proceed with surgery, they can arrange that.

    This is what any surgeon would say. It's pretty normal. Cataracts are not a life threatening condition and the surgery is extremely low risk now so they no longer have to wait until you are almost blind. So it's really up to you and they will never tell you that you NEED surgery. They're also always wary of course about being blamed for poor outcomes so again unless you are almost blind or it's a life threatening condition they are nit going to say you NEED it. For that matter, even if it was life threatening the ultimate decision is still yours.

  • RonAKA
    RonAKA sam36130

    Edited

    Sam, thanks to @ka76787 finding more information about the power range of the enVista, I see that the lens is available in 1.0 D steps in the range from 0.0 D to 10.0 D. If I recall correctly I think you said your required lens power had been predicted to be in the 8.0 D range. The good news is that the enVista is available in that power range, but the bad news is that it is in 1.0 D steps which are quite large and will give about 0.75 D steps in power outcomes. If you get to see your IOL power calculation sheet there is usually a line at the bottom of the power steps that predicts the theoretical perfect power needed to achieve the target. That line will show what the ideal power is, even though that exact power does not exist. But, it can help you decide if the enVista steps in power are too large and whether your power need would be better suited to the 0.5 D steps that are missing in this particular lens model. For example the Alcon Clareon lens which is also very good is available in 0.5 D steps from +6.0 D to +30.0 D. It is possible depending on your specific eye measurements that a Clareon lens in a half step in power would be a better fit for you. And, of course it is possible that one of the even number full steps in the enVista is the perfect fit for you. The IOL Calculation sheet will be the key in determining that. Both eyes of course are unlikely to be the same and have the same power requirement.

    .

    Something to think about when you have your next clinic visit. In a perfect world it would be ideal to see what the Hill-RBF 3.0 formula predicts for both the enVista and Clareon lenses. I believe the IOLMaster 700 can do that, if that is the instrument they are using.

  • jo61855
    jo61855 sam36130

    Posted

    If there isn't too great a power difference of the lens, you should be okay. I have a 1.00D power differential, and my binocular vision is good. I am slightly far-sighted naturally, and have the EDOF Vivity lenses.

    • sam36130
      sam36130 jo61855

      Posted

      Jo,

      What were the targets for both eyes? was the 1.00D between eyes planned or from the fluctuation/refraction errors after surgery? what distances can you see clearly and blurry?

    • jo61855
      jo61855 sam36130

      Posted

      The targets were 20/20 or 20/25. My results were 20/20 for the LE and 20/25 for the RE I was told that my RE operated on June 29th was dominate and set for distance. I asked for slightly more near vision for the second surgery on July 10th, and that is what I got. Glad it turned out that way. I went with Vivity lenses for distance, intermediate, and functional near. Vivity lenses, however, are not recommended for several conditions by Alcon.

  • RonAKA
    RonAKA sam36130

    Edited

    Sam, I am not sure where you are at with your cataract surgery process, but I have done some playing around with the eye measurement numbers you have supplied. The K1 and K2 numbers are missing for your right eye, but I have the rest and have estimated the missing K1 and K2 values from your left eye values. Your eyes appear to be very similar. What I am seeing is that probably the ideal power for distance vision in both eyes is +8.5 D. And the ideal power for targeting -1.5 D in either eye for mini-monovision is probably +10.5 D. So, if the enVista is really only available in even number powers below +10.0 D then they would not be an option for the +8.5 D lens. However, the second choice may be a +8.0 D power for distance vision. The Barrett and EVO formulas both estimate a -0.11 D slight myopia with an 8.0, while the Hill shows a slight hyperopia at +0.07 D. I guess if one takes them all together then the +8.0 D may be worth the risk. A -0.11 outcome would be essentially perfect, and even a +0.07 D would not be bad. And if you are considering monovision the enVista is supposed to be available in a +10.5 D power.

    .

    If you can supply the K1 and K2 values for the right eye, I can confirm these numbers, but it would be a bit surprising to see it change much.

    .

    Edit: I just ran the OS left eye measurements in the Kane formula and got a prediction of -0.06 D for a +8.0 D lens. The Kane formula is quite easy to use and is one the better ones. All considered these formulas are giving pretty consistent results for your eyes.

    .

    From the Kane site:

    "Multiple published clinical studies have demonstrated that the Kane formula is more accurate than all currently available IOL formulas (including Hill-RBF 2.0, Barrett Universal 2, Olsen, Haigis, Hoffer Q, Holladay 1, SRK/T, EVO and Holladay 2)... The Kane formula maintains its accuracy at the extremes of axial length, resulting in a 25.1% reduction in absolute error in long eyes (≥26.0 mm), compared with the SRK/T"

    .

    Note that Hill-RBF formula has been updated to the 3.0 since these quoted studies were done.

    • sam36130
      sam36130 RonAKA

      Posted

      hi Ron,

      Your response to my R eye K1&K2 values wasn't posted.

    • RonAKA
      RonAKA sam36130

      Edited

      I posted the results as an image, so it went into moderation, and should show up tomorrow. The short story is the Hill 3.0 results are:

      .

      Target distance (-0.25 D)

      OD Right eye

      +9.0 D +0.04 D

      +9.5 D -0.28 D

      OS Left eye

      +8.0 D +0.07 D

      +8.5 D -0.25 D

      .

      Target near (-1.5 D)

      OD Right eye

      +11.5 D -1.61 D

      OS Left eye

      +10.5 D -1.56 D

    • RonAKA
      RonAKA sam36130

      Edited

      Sam, I don't know what the problem is, but my detailed response to you with the Hill 3.0 results remains in moderation at the bottom of page 2 of this thread. I sent you a PM suggesting alternate ways to get the information to you, if you check your messages inbox. What you may want to do is try using the Kane IOL Power Calculation Formula. It is giving very similar results to the Hill 3.0 formula. And, it seems to run fine with the Chrome brower. Some tips in using it for your numbers:

      1. Select your gender
      2. Enter 119.2 in the A-constant field (that is for the enVista lens)
      3. Don't select a lens in the IOL type
      4. Enter -0.25 for a target to see results for distance.
      5. Enter all the rest of your values. It is not necessary to enter the axis numbers for K1 and K2
      6. Then click on Calculate. It will take several seconds to give you results

        .

        As a check I got a recommended lens of +9.5 D for the right eye with a predicted refraction outcome of -0.36 D. For the left eye the recommended lens is +8.5 D with the same predicted outcome of -0.36 D. Unfortunately I don't believe the enVista lens is available in those half dioper powers. The Clareon lens is. The results for the Clarion are almost identical. To see them change the A-Constant to 119.26 and recalculate.

        .

        The table of outcomes displayed will show your other options for even power values.

        .

        And if you want to see prediction for a near eye just change the target to -1.50 D and recalculate. This pushes you up into the range of powers that the enVista supplies in 0.5 D steps. Bottom line is that if you do one near eye, you can get a good outcome with the enVista lens. But, for the distance eye, there are some decisions to be made if you use the enVista, due to the lack of half diopter power steps.

        .

        And on one last point I ran your numbers through the Kane Toric Calculator and the predicted residual astigmatism is very small. You certainly do not need a toric lens.

        .

        Edit: Make sure you put a minus sign in front of your target diopters. And if you are serious about going more myopic as your surgeon is suggesting then enter a target of -0.5 D. What I see predicted is a +10.0 D lens in the right eye with a predicted outcome of -0.67 D. And a +9.0 D lens in the left eye with the same predicted outcome of -0.67 D.

    • sam36130
      sam36130 RonAKA

      Posted

      thank you Ron. i will check with the surgeon about the lens power if possible tomorrow. i believe at this point, i have to trust his specialty to avoid hyperopia and be a touch myopic.

    • RonAKA
      RonAKA sam36130

      Posted

      If there are no half power steps below +10 D for the enVista it leaves you in a bit of a tough choice situation. I'm convinced based on all the numbers I have seen that a +8.5 D is the right choice and will leave you myopic by about -0.25 which is ideal. However, if half powers are not a choice, then you would have to decide between +8.0 D and +9.0 D. A +8.0 D is going to leave you an insignificant amount hyperopic, while the +9.0 D is going to leave you more significantly myopic in the -0.5 D to -0.75 D range.

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