Understanding IOL Calculation Sheet
Posted , 4 users are following.
I asked for my IOL Calculation sheet from the surgeon today and now I need to try to understand it. Thanks to RonAKA I went online and input the data to see if the calculations were the same. There are 2 columns on the sheet I received from the surgeon, one says IOL (D) 21.00 and the other column says Eye (D) -.0.55 that's for my right, non-dominant eye. Does this mean the power of the lens will be 21? What does the -0.55 mean? My left, dominant eye says IOL (D) 20 and Eye (D) -0.10. Thanks.
0 likes, 9 replies
karin08666
Posted
Sorry, should have added the online calculator was the same as the one I received from the surgeon
RonAKA karin08666
Posted
Guessing a bit, but an IOL lens power of 20 or 21 would be approximately what would be used for someone that was mildly far sighted. And another guess would be that the -0.55 D, and -0.10 D are the predicted residual sphere values.
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Normally there are two columns of numbers; IOL (D) and Eye (D). The IOL (D) column should be a range of IOL powers that are close to what you need, and the EYE (D) is the predicted residual refraction outcome. The other thing to watch is there should be a place where you enter the target outcome. Some will target 0.0 D or plano, while others will target -0.25 D for distance. And if the objective is the near eye in mini-monovision the target may be -1.5 D or so. This is for non toric lenses. If you are using a toric then there should be additional columns which give the cylinder values and SE values which is the spherical equivalant of the residual sphere plus cylinder.
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Have you tried the Hill-RBF 3.0 Calculator? Did it predict the same power as your surgeon is predicting?
karin08666 RonAKA
Posted
If a power of 20 or 21 is for someone mildly far sighted, that is odd. I am near sighted, I take my prescription glasses off to read. My last prescription was RE sphere -2.00 and LE sphere -2.50.
I tried the Hill-RBF calculator, but it wouldn't let me enter information. Not sure why. I found another one which listed a number of calculations you could use Hill and Barret being 2 of them. They came up with the same powers that were highlighted on my surgeon's calculation sheet, however, my surgeon ticked off the 21 power for my right eye instead of the 20 that was highlighted. Again, not sure why.
According to my surgeon the RE is IOL (D) is 21.00 and EYE (D) is -0.55. LE is IOL (D) 20 and EYE (D) -0.10.
I will find the calculator I used and try entering the information again as I did not enter a target outcome.
RonAKA karin08666
Posted
Some surgeons leave the target set at plano, but then select a different power lens than the one recommended for plano, to give the predicted result they want to target. I recall you wanted to be left with -0.5 in the right eye, and -0.25 in the left.
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Not sure why you would have trouble with the Hill formula on line. I have used it, and it worked OK. I wonder if there is a specific field you are not filling in.
karin08666 RonAKA
Posted
RonAKA you were correct, my surgeon did leave the target blank and then picked the one that would work with what he wanted. I entered the target on the Barrett calculator and it was pretty much bang on with what he picked. My left eye is my dominant eye so the target will be -.25 and then my right eye will be -.50.
This is a different question, but on my IOL Calculation sheet it shows under the iris barycenter and pupil barycenter my right eye is -0.39 and -0.21 respectively and my left eye is 0.26 and 0.35. Could this be the reason I am slightly nearsighted? Some reading I have done seems to suggest this. I thought my axial length might be longer because of being nearsighted, but it is "normal".
I find all this very interesting and learning how all this works takes my nervousness about this process away. Thanks for your help, much appreciated.
RonAKA karin08666
Posted
I checked back in my file to see what I got for IOL powers, as my eyes were mildly myopic in the -1.5 to -2.0 range. My first eye used a 15.5 D power. The second was a 18.5 D, but in that eye I was targeting -1.25 D or so for mini-monovision. If it was fully correcting the myopia the power required would have been closer to 16.5 to 17.0 I would expect. I unfortunately at the time did not know enough to ask for the calculation sheets.
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I recall you were planning on getting a toric lens in the left eye. Did they do that, and have they predicted residual cylinder? That is the other wild card. If they did not use a toric then the power used for the sphere will likely be adjusted to try and correct some of the astigmatism.
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I have used the Hill formula a few times for my brother's surgeries and it worked. I will try running it again today to see what might be the issue.
RonAKA karin08666
Posted
I had a go at running the Hill-RBF 3.0 formula again. I see that it is quite picky about the data entered or not entered. It seems to want the birthdate of the patient and in the right format as I found out, and it also seems to want you to enter the A constant manually despite what it seems to indicate. I believe the A constant for the Eyhance is 119.3 based on what I found with a google search for specifications. Not sure it even uses the manufacturer and lens model data. The calculator highlights fields that it is rejecting or wanting in red, so you can't run the calculator until those fields are happy... What I did notice though is that I am not sure this calculator can be used for toric lenses. However, I am entering data for my brother who does not need a toric, so I'm not sure about that part. With the Barrett formula I believe there is a separate calculator for toric lenses.
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The Hill-RBF formula is very sophisticated in that it was developed using artificial intelligence. The surgeons using it apparently submit data back to Dr. Hill and the formula is refined using artificial intelligence based on the measurement data and the actual outcomes the surgeons achieved. I noticed that it is giving slightly different outcomes (but not significantly different) from what it was a few months ago. the current version seems to be 3.0.2. It may use seemingly irrelevant data like age and sex if the AI model determines it improves the prediction accuracy. I have not played with it enough to test if changing those inputs actually change the predication though...
karin08666 RonAKA
Posted
When I had my eyes measured the first time it showed an astigmatism in my left eye of 1.14. I asked for my eyes to be measured again and my left eye showed .7. My surgeon said he wouldn't use a Toric lens because the astigmatism wasn't significant enough (I believe it has to be over 1 for a Toric lens), he would just put his incision in a place that would reduce the astigmatism. About 3 years ago my new glass prescription was giving me problems. My optometrist took out the astigmatism correction and I was fine. I think perhaps the shape of my eye changed due to age and therefore perhaps my astigmatism did too.
Just out of curiosity I will maybe give the Hill calculator another go and see if it is the same as Barrett.
RonAKA karin08666
Posted
0.7 D cylinder if measured at the IOL plane is right on the margin of being correctable with an IOL, but only if it is available with 1.0 cylinder. At the reference cornea or eyeglass level this is the value required to correct 0.7 D at the lens plane. However, of the common lenses I believe only the AcrySof IQ and enVista are available with a 1.0 Cylinder. The Clareon and Eyhance are not, and 1.5 D is the minimum, and for you that would be too much.