Intraocular Lens Power Calculation For Eyes With A History Of Myopic Laser Keratorefractive Surgery: A Comparison Of 7 Formulas.

This comparative study aimed to compare the prediction accuracy of current no clinical history post-laser refractive surgery intraocular lens power calculation formulas.

Tan Tock Seng Hospital, Singapore

One hundred and forty-eight eyes of 87 patients were included in this study.  All eyes had previously undergone myopic LASIK or PRK.  IOL power calculations were performed retrospectively using preoperative data from the IOLMaster 700 biometer. The IOL power formulas used either standard keratometry (Barrett True-K, EVO, Haigis-L, Shammas-PL) or total keratometry values (Barrett True-K TK, EVO TK, Haigis-TK).  Refractive prediction errors were calculated based on the predicted postoperative refraction given the implanted IOL power, and the achieved postoperative manifest refraction. 

The mean absolute error (MAE) was 0.465, 0.438, 0.435, 0.414, 0.570, 0.472 and 0.571D and median absolute error (MedAE) was 0.383, 0.348, 0.348, 0.305, 0.528, 0.372 and 0.499D for Barrett True-K, Barrett True-K TK, EVO, EVO TK, Haigis-L, Haigis-TK and Shammas-PL respectively.  EVO TK and Barrett True-K TK achieved the highest percentages of patients with absolute prediction error within +0.25 and +0.50D (42.57%, 69.59% and 37.84%, 68.24% respectively). Pairwise post-hoc analysis revealed differences in absolute prediction error for: EVO vs Haigis-L, EVO vs Shammas-PL, EVO TK vs Haigis-L, EVO TK vs Shammas-PL, Barrett True-K vs Haigis-L, Barrett True-K vs Shammas-PL, Barrett True-K TK vs Haigis-L, Barrett True-K TK vs Shammas-PL (p<0.001).

Adding posterior corneal power measurements improves predication accuracy of post-LASIK IOL power calculations.