Got My IOLMaster printout. How to interpret? What's useful to me?

Thanks Ron,

I looked at that guide. On the diagram of the printout the area with delta k is labelled "11" and "11" on the next page is described as "k flat, k steep and cylinder." On mine, the number next to delta k is 6.77 d, followed by an axis number in degrees, and up top in the notes preceded by the exclamation point, it says right eye, high astigmatism, 6.77 cylinder. So this all points to delta k being the cylinder. The numbers match (6.77), its followed by "d" and then an axis figure, and the key says cylinder is in that area.

A google search turned up an article that used delta k and cylinder interchangeably, by implication: "With this patient, I looked at her Delta K and it was 0.53 D. Typically, I treat cylinder between 0.50 D and 1.0 D with a limbal relaxing incision (LRI) and anything over 1.0 D with a toric IOL..." but in this case the writer decided against the LRI, she said.

So, I think delta k is the cylinder.

The delta K (keratometry ) number in diopters is the measure of anterior corneal astigmatism. Some ophthalmologist see value in also getting delta TK (total keratometry ) and that is the combined measurement of both anterior and posterior corneal astigmatism to be corrected. On mine, the delta TK value was greater than the delta K value.

I have a recent IOL Calculation sheet from my brother that I have been trying to help him with. I never got one for myself. In any case this is what I see on my brother's sheet for the right eye:

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Delta K +0.91 D @ 85 deg

Delta TK +0.7 D @ 79 deg

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And then lower down with a toric lens selected with no cylinder, and using the Barrett TK formula these numbers:

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Ref Cylinder 0.31 D @ 74 deg (which I understand to be at eyeglass plane)

IOL Cylinder 0.46 D @ 74 deg (IOL plane Emmetropia)

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I gather these last two are the expected residual cylinder values when using a non toric lens. As it is not enough for a toric, he is not getting one. All kind of convoluted, as to get these numbers the surgeon seems to select a toric lens so the residual gets calculated. Using the actual lens he will get which is higher up, there is no predicted values given. With the non toric lens a power of +14.5 D is predicted. But, with the toric lens selected a power of +15 D is predicted, and is the power the surgeon is saying he will use. It seems as if he is over correcting the myopia and depending on the residual cylinder to give net reference sphere of -0.17 D, and spherical equivalent of -0.01. I worry that he may be cutting it a little close and there is a risk of coming out positive.

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In any case I don't see anything really lining up on the cylinder to the delta K. They are in the ballpark but not the same. I believe his true residual cylinder and astigmatism at the eyeglass plane is 0.31 D.

Wouldn't+15D be less correction than +14.5D? 19D or so is the least amount of correction so 19-15=4 vs 19-14.5=4.5.

It's interesting that there's a fictitious 0.46 D toric entered in. Confusing but interesting and maybe a clever way to get a Ref SE prediction. I wonder how one would remove the effect of the 0.46 D toric from the prediction later.

Yes, that is correct. The 15 D would leave more sphere myopia. I find the cylinder portion very confusing, along with how it is used to calculate SE. I have discovered that ophthalmologists like to express astigmatism as a "+" number compared to optometrists who write Rx numbers as a "-" value. And you can convert a ophthalmologist number to an optometrist number by simple reversing the sign, and adding or subtracting 90 degrees to get a value between 0 and 180 degrees. This kind of makes sense as one convention is measuring the angle to the steepest part of the while the other is to the least steep. What is less obvious is that astigmatism is assumed to increase myopia and ability to read. In other words it is assumed to be a negative that adds to the myopia which is negative. Not sure why that is, as astigmatism has an equal and opposite positive side to it. But, all of this is confusing when you calculate spherical equivalent.

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Which leads me to a question for you. If I was to PM you with a copy of my brother's IOL Calculation would you be willing to give me your thoughts on this aspect and what it means.

Yes of course. I doubt I can help though because most of what I've learned came from your posts and Bill's posts and other posts here.

I lacked the courage to go against the surgeon's advice in the end for myself.

There are some suggestions that the Barrett Universal II and Hill-RBF 2.0 are among the most accurate for long eyes. Other formulas require specific adjustments for long eyes.

What is the objective with the targets?

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If you want distance vision without glasses then the normal target is -0.25 D. Also with the left eye it seems like far too much of an offset for normal reading ability without glasses. With an Eyhance an under correction of -1.0 to -1.25 would be more reasonable. Or, it could be another monofocal targeted to -1.5 D.

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Also would you not benefit from a toric in your left eye as well as your right?

The objective is the best close and intermediate vision. Also, very close vision without glasses. Also, protection against hyperopic surprise.

Factors to consider:

1) Presently I have prism in my glasses prescription. The diplopia may be a result of my strong and differing lenses, so it may go away, but it may not. If it doesn't I'll have to wear glasses for that anyway.

2) I value my good extreme close-up vision, a gift of the myopia. I don't want to lose that. If I target distance, then I have to put on glasses for closeup at some distance for tiny things. I'd rather take them off for extreme closeup. You never know where or when you'll need extreme closeup vision, so if you don't have it with the naked eye, you have to carry readers. The need for distance vision is more predictable. I can keep distance glasses in the car and by the TV.

3) I have very long eyes. Hyperopic surprise is a bigger risk with long eyes.

4) Yes, it would be a toric Eyhance

OK, I see what you are doing. It would not be my choice as I find my least required vision is extreme close up. That is the only time I need help with readers. But, yes if intermediate and close vision without glasses is a priority then setting both eyes for that range can make some sense. It still would be a good idea to put a differential between them to cover a wider range. If it were me I would stick to the lower risk monofocals instead of Eyhance. The advantage of Eyhance is a flatter curve off to the right on the defocus curve. When you target a large offset that advantage is kind of wasted, or at least becomes insignificant.

It won't be a fair test, because the Zeiss goes into an eye with a very non-spherical cornea and a bit of a wrinkle in the mild epiretinal membrane while the Eyhance goes into an eye with a close-to-spherical cornea and a mild epiretinal membrane that's pretty smooth. But yes, it will be interesting, if I go that route. I still want the IC-8 instead of the Eyhance and might change the targeting from what has been recommended to me. I plan to hold out for at least another year before doing surgery, so there's time for lots of plans to change.

Now that I know about the Fixoflex, I want that too, so there's reason to wait even longer. It sounds like I might have to go to Europe for both eyes. A month or two on an idyllic Greek isle doesn't sound too bad. (The inventor of the Fixoflex practices on Crete and some of the clinical trial is being done there; the other site is Alexandria, Egypt.) They are predicting CE Mark approval and rollout in select markets in 2023. I guess that means mark your calendar for 2030 for FDA approval and rollout here.