For axial lengths from 22.50 mm to 24.00 mm, and central corneal powers ranging from 42.00 D to 45.00 D, and a normal anterior chamber depth, most modern IOL power calculation formulas will give good outcomes. However, for eyes outside this range, our results indicate that Haigis (with properly optimized a0, a, 1, and a2 constants) and the newer generation formulas, such as Holladay 2, Olsen, and Barrett, yield better results.
The chart above represents our experience with popular IOL power selection methods, where measurements were made using optical biometry. We are now using only the Barrett Universal II formula and the Hill-RBF pattern recognition method for all of our calculations. For individuals with high to extreme axial myopia, we will also examine the Wang-Koch axial length modification of the Holladay 1 formula. Eight years of experience have shown that the best pre-operative measurements have been with the Haag-Streit Lenstar.
For Holladay 1, SRK/T, Haigis, and Holladay 2, an adjustment is required for the high to extreme axial myope and axial lengths above 25.00 mm. How to do this is outlined at:
The Journal of Cataract and Refractive Surgery paper that describes this approach can be found at:
- Wang L, Koch DD. Modified axial length adjustment formulas in long eyes. JCRS 2018; 44:1396-1397.
Here is something to consider. As surgeons, we are now primarily judged by our patients and peers based on our refractive outcomes. It seems a little odd to spend tens of thousands of dollars on the next most accurate measurement technology, but continue to rely on calculation methods that are not from this century. Optimal outcomes require the most precise measurement technology and the most effective calculation methods.
