Accuracy of recent intraocular lens power calculation methods in post-myopic LASIK eyes

Abstract

This retrospective study compared postoperative prediction errors of recent formulas using standard- or total keratometry (K or TK) for intraocular lens (IOL) power calculation in post-myopic LASIK patients. It included 56 eyes of 56 patients who underwent uncomplicated cataract surgery, with at least 1-month follow-up at Keio University Hospital in Tokyo or Hayashi Eye Hospital in Yokohama, Japan. Prediction errors, absolute errors, and percentage of eyes with prediction errors within ± 0.25 D, ± 0.50 D, and ± 1.00 D were calculated using nine formulas: Barrett True-K, Barrett True-K TK, Haigis-L, Haigis TK, Pearl-DGS, Hoffer QST, Hoffer QST PK, EVO K, and EVO PK. Statistical comparisons utilized Friedman test, Conover's all-pairs post-hoc, Cochran's Q, and McNemar post-hoc testing. Root-Mean-Square Error (RMSE) was compared with heteroscedastic testing. Barrett True-K TK had the lowest median predicted refractive error (-0.01). EVO PK had the smallest median absolute error (0.20). EVO PK had the highest percentage of eyes within ± 0.25 D of the predicted value (58.9%), significantly better than Haigis-L (p = 0.047). EVO PK had the lowest mean RMSE value (0.499). The EVO PK formula yielded the most accurate IOL power calculation in post-myopic LASIK eyes, with TK/PK values enhancing accuracy.

Keywords: IOL calculations; IOL power calculation; Post-LASIK IOL calculations.

Fig. 1

Prediction error (D) for each formula. Results were compared using Friedman testing and Conover’s all-pairs testing with Holm adjustment to determine statistically significant differences. D = diopter. p < 0.05, For full explanation of statistically significant findings, please see the Results section in main article text. Horizontal lines indicate statistically significant relationships between formulas.

Fig. 2

Absolute prediction error (D) for each formula. Results were compared using Friedman testing and Conover’s all-pairs post-hoc testing with Holm adjustment to determine statistically significant differences. D = diopter. p < 0.05. The EVO PK had a significantly lower absolute error compared to the EVO K (p = 0.003), the Haigis-L (p = 0.026), and the Hoffer QST (p < 0.001). Horizontal lines indicate statistically significant relationships between formulas.

Fig. 3

Prediction accuracy within ± 0.25 D, ± 0.50 D, and ± 1.00 D for each formula. Percentages were compared using Cochran’s Q testing and McNemar post-hoc testing with Holm adjustment to determine statistically significant differences. D = diopter. p < 0.05 The percentage for EVO PK was significantly greater when compared to the percentage of eyes within ± 0.25 D predicted by the Haigis-L (p = 0.047), as indicated by the horizontal line. There was no statistically significant finding when comparing between the formulas with post hoc analysis for the percentage of eyes within ± 0.50 D and ± 1.00 D. Synopsis: The EVO PK formula yielded the most accurate results for IOL power calculation in eyes with previous myopic LASIK surgery. Utilizing TK/PK values might further improve the overall accuracy.