Cataract Surgery IOL target for second non-dominant eye
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I am a 65 yo farsighted female with history of a slight astigmatism in both eyes who has worn progressive lenses for 30+ years until diagnosed with cataracts 4 years ago after which I switched back to bifocals set for distance and comfortable relaxed bent arm cellphone use. I hesitate to call it intermittent because many view that as full arms length. i have found it very rare when I really need to read something up close or super tiny.
Thirteen days ago I had cataract surgery on my dominant left eye with IOL set to distance; my astigmatism was also corrected via laser. I received the Tecnis IOL (ZCB00) with Diopter +20.5d. My LE is doing great. At day one post-op I was easily reading 20/20 and by day the 10 post-op, 20/15 was crystal clear and I could read the 20/10 line even though it was not as clear.
I am currently scheduled to have my non-dominant right eye done 2 weeks from tomorrow. The plan is to make RE slightly nearsighted to try and make it such that I will be able to use my cellphone & iPad without glasses. He is planning to put in Eyhance IOL (ICB00) with -1.25 target. He said something about aiming maybe some place shy of -1.25, so in reality it would be between -1.0 and -1.25.
I understand the concept of what he is attempting to do, but I really do not understand the numbers cited above, as they seem to be very different. I do not know if I have given enough info, but if so, can someone explain those numbers to me. And, does this RE target seem like it should allow me to operate without glasses from about 16” for cell and 20" for iPad?
He mentioned during pre-surgical for the LE that he would have to see during my second post-op what I could handle in my right eye, presumably based on how well or not my LE did. At that time he seemed to be suggesting that the target would be either a -1.25 or -1.50. So I do not know what made to shift to between -1.0 and -1.25. Can anyone shed any light on that as well?
I am okay with needing readers for the rare time that i might want to read tiny print closer than 16". I would, however, not be happy, if it ended up that i had to constant put on readers just to read a text or send one or to read things on my iPad.
Any insight would be appreciated. Thanks
0 likes, 25 replies
zippet
Posted
Thanks for that. So it is as we suspected, that his -1.25 game plan with a possible range between -1.00 to -1.25 is the way to go, as to go with -1.50 would cause too much of a trade off at the far end. I'll let you all know how I make out with my RE. Its been very helpful be able to talk this out with others. Again, thanks a bunch.
RonAKA zippet
Posted
While my other post is being moderated I will point you to an article that includes a defocus curve graph for the Eyhance and the standard Tecnis 1 (that you have now in your right eye). Search for this article title and you should find it.
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Review of Ophthalmology 15 April 2021 IOL Review: 2021 Newcomers
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Skip down to the graph that shows Defocus curves for Tecnis 1 and Eyhance. Focus on the LogMar horizontal line for 0.2. This is an estimated vision acuity of 20/32, so not perfect but good. This horizontal line intersects the blue defocus curve for the Tecnis 1 (the lens you have) at -1.0 D. This translates to 40" divided by 1.0 or 40" distance. You say you have good vision at 30" which is better than the defocus curve predicts. But, also look at the vertical bars with the flat tops and bottoms. That indicates the range of actual people tested. So some are getting much better than the curve and some much less. The people that got the very best result got out to a defocus position of -1.5. So that translates to 40/1.5 or about 27" which is slightly better than what you got.
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Next look at the blue bar which represents the Eyhance. There is no error bars just a single line, but keep in mind actual results could be similarly above or below this blue line. The blue line gets you out to -1.5 or 27" on average, rather than the best case. It adds 0.5 D to the defocus curve.
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Next if you target myopia instead of perfect vision this whole curve moves to the right. Targeting -1.0 of myopia for example moves you out to the -2.5 position at a LogMAR of 0.2 or 40"/2.5 or 16". Targeting -1.5 myopia moves the curve out to the -3.0 D position or 40/3 = 13.3".
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This particular graph does not go that far to the left to allow you to estimate loss of distance vision, but in a previous post I gave you that estimate from another graph. You can see from the graph that the part to the left of the 0.0 defocus position is steeper and and the Eyhance is no better than the standard lens. That means the more myopia you target the negative impact is larger on distance vision than it is on close vision.
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Hope that helps some.
zippet
Posted
Hi all. I have updates. But first, before me, a bit of good news…
After a week of extensive testing, my husband’s imaging irregularities seems to show upon further evaluation that he has developed a substantial hernia near his hepatic pump that was obstructing a good view of things on the initial imaging. Given this, he has been immediately schedule for surgery for next week. His surgeon believes he will be able to make the repair without needing to remove his pump. This would be good and it is a major relief. If all goes well, he should be home for Thanksgiving. Now on to me…
I am home now, after having had my right eye done earlier today. Of course I really can’t tell anything yet as my eye is still dilated and such as well as bandaged with one of those eye shields. Tomorrow I will go for my day one post-op for my right eye. That being said, I can report that my implant identification card says my right eye received the following lens - Model: DIB00, Diopter: +22.0D. As a reminder, three weeks ago my left eye received - Model: ZCB00, Diopter: +20.5D. I don’t know what these numbers mean, so if anyone can shed any light upon this, that would be great.
As always, thanks for all your incites and thank you once again for all your well wishes. All were greatly appreciated.
rwbil zippet
Posted
I have actually looked over IOL Master Measurements and have become familiar with many of the Measurements like Axial Length (AL) and Steepest and Flattest K for Astigmatism, but Power calculation is a bit more aloof to me.
I can tell you AL is important to calculating power and it gets trickier if you have short or long eyes. But in simple terms that is the IOL Power needed to hit Plano or Emmetropia (assuming that was your refractive goal).
RonAKA zippet
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First, good to hear that your husband's prognosis is improving. All the best to both of you.
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" I can report that my implant identification card says my right eye received the following lens - Model: DIB00, Diopter: +22.0D. As a reminder, three weeks ago my left eye received - Model: ZCB00, Diopter: +20.5D."
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The DIB00 lens is the Eyhance one. The other number for the Eyhance is ICB00. I suspect the difference is not in the lens, but in the delivery system to get the lens into the eye.
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The ZCB00 is the standard Tecnis monofocal lens.
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A short while ago I stumbled onto an article that talked about how the power of lens needed is calculated. Today this is a very technical and complicated process of detailed measurements, computer calculations using different formulas, and experience based decisions. However, according to the article, the state of the art in the mid 1970's was to simply take a power of 19 D and add the eyeglass spherical prescription (prior to developing the cataract) to it. So say for example a few years before the cataract developed the eyeglass prescription was -4.0 D spherical. You would add that to the 19 and get an IOL power of 15 D. This tells me the method is based on a 19 power IOL would be a neutral one that would be used on someone that had no spherical error in the eye that needed to be corrected.
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So based on that 1970's method and your previously posted prescription of +2.25 for both eyes. that would translate to an IOL power of 21.25 D. However that is a very ballpark number. Methods are much more sophisticated today, and they were targeting as I recall -1.25 myopia in the near vision Eyhance eye. That would change the power too of course. About all you can tell from this is that your eyes must have been far sighted, and the lens power is in the ballpark. The acid test for determining if the lens power is correct is the refractive eye test done by an optometrist - or your eyeglass prescription. The perfect outcome would be 0.0 D in your left dominant distance eye, and -1.25 D in your right closer eye. The refractive test will tell you where you really are, and if there is any residual astigmatism. And you need 6 weeks after surgery to get a stable final outcome.
lucy24197 zippet
Posted
The Diopter you show is the power of the IOL itself. Based on the shape & dimensions of your eye, the surgeon looks at several calculations to see what power of IOL is needed to hit the desired target for a particular eye. It varies from person to person--a bit like a prescription for a glasses lens, but inside your eye. In my case, I have the exact same IOL in both eyes--a ZCB00 with a diopter of +22. Due to the differences in my eyes, after surgery one eye ended up at -0.5 and the other ended up at -1.75--both were right on target. It was interesting hearing the surgeon and nurse talk before the surgery of my second eye. They discussed 2 equations for my eye. One equation predicted this lens would put me at -1.72, the other said -1.98. So not only do they look at different lens powers, they look at different calculations predicting outcomes for a particular lens--a good & knowledgeable surgeon really helps!
And so glad to hear that you got good news regarding your husband. Hope his surgery goes well and that your eyes continue to improve, and that you both have a wonderful Thanksgiving!
zippet
Posted
Thanks for the incites. Just curious, are these the two numbers I have read that people use to determine the difference between the eyes and hence whether or not one has full, mini, or micro vision? Or, are those two other numbers? That’s something I have not been able to figure out as so many numbers get bantered about and mixed and mingled.
I’m glad to hear that that sort of refractive evalaution isn’t for like six weeks as our plate is going to be quite full. Next week is my husband's surgery, the week offer my second RE post-op, and the week after that my husband’s staples get removed. Both offices have said they will work around both of our subsequent follow-ups. So I guess I'll see what they are as things unfold.
RonAKA zippet
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"are these the two numbers I have read that people use to determine the difference between the eyes and hence whether or not one has full, mini, or micro vision? Or, are those two other numbers? "
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No, you can't really use the powers of the IOL's to determine the amount of monovision you got. If your eyes were identical, you could, but it is highly unlikely that your eyes are identical. Your older eyeglass prescriptions look near identical. But, keep in mind that eyeglasses have to correct error in both the cornea and your natural lens. With the lens removed and replaced with an IOL the IOL only has to correct for the error in the cornea. It is not likely the cornea error is identical. You are best to wait for the refractive exam 6 weeks post surgery to get those more accurate numbers.
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You should however be starting to get some indication of the results based on what you can see. The ZCB00 eye should be giving you excellent distance vision but not too good close up. The DIB Eyhance should be giving you much better close vision and reasonable distance vision. But, it takes time for the eye to recover from the surgery, and there is likely to be swelling that is impacting how well you will be able to see for a while.
zippet
Posted
Gotcha. Just curious, do you know if there is a tendency for the distance eye to typically show corrective results sooner than the eye corrected for mid-range? My thinking, which might be out in left field, is that may that typically is the case as dominant distance has more play in range to notice something than the more finely tuned smaller range of focus for the non-dominant mid-range eye that also has to over come the brain getting accustomed to that eye being used only for the closer stuff. Does this logic make any sense? Or, it doesn't and noticing results is just random with no typical pattern?