IOL calcs with steep corneas

[90 diopter]

There's a good amount of literature out there on IOL calculations on patients with either very long or very short axial lengths, but I can't locate any good information regarding calculations on patients with abnormally steep or flat corneas. I've noticed in patients with K's at one extreme or the other, there is a significant difference in IOL targets depending on whether one uses Holladay 1/2, SRK-T, or Hoffer Q; one formula might recommend a +16.0 to hit plano, while another might recommend a +17.5.

Does anyone know if any formula is more accurate than the others in this situation?

---

Members don't see this ad.

 

[guttata]

Questions

1. How are you obtaining the Ks?

2. How steep and how flat are the Ks?

3. Why are the Ks steep and flat? KCN? RK? LASIK?

With prior refractive surgery (LASIK/RK), I would use ASCRS' calculator.

With RK, I target more myopia (around -1.00) since there can often be a hyperopic surprise (even after using the calculator). With KCN, it probably doesn't matter because you won't be able to correct the irregular astigmatism without a CL. But, I would err on the side of more myopia.

 

[90 diopter]

1) A combination of the auto-refractor, manual keratometry, and orbscan.

2) In my most recent patient, Ks are 49.00, 48.00

3) Ks are naturally steep. Patient is a myope with steep corneas and an average axial length. No prior surgery.

I do use the various tools and formulas in patients with prior corneal surgery. I'm specifically wondering in patients with naturally abnormal K values, which formula provides the most accurate and reliable IOL calculations. Usually there ends up being a significant difference among all the formulas, and I end up averaging all of them and aiming myopic. Maybe I'll do a retrospective study to look at this, though my personal sample size is pretty small.