Accuracy of 14 intraocular lens power calculation formulas in extremely long eyes

Purpose To compare the accuracy of 14 formulas in calculating intraocular lens (IOL) power in extremely long eyes with axial length (AL) over 30.0 mm. Methods In this retrospective study, 211 eyes (211 patients) with ALs > 30.0 mm were successfully treated with cataract surgery without complications. Ocular biometric parameters were obtained from IOLMaster 700. Fourteen formulas were evaluated using the optimized A constants: Barrett Universal II (BUII), Kane, Emmetropia Verifying Optical (EVO) 2.0, PEARL-DGS, T2, SRK/T, Holladay 1, Holladay 2, Haigis and Wang-Koch AL adjusted formulas (SRK/Tmodified-W/K, Holladay 1(modified-W/K), Holladay 1(NP-modified-W/K), Holladay 2(modified-W/K), Holladay 2(NP-modified-W/K)). The mean prediction error (PE) and standard deviation (SD), mean absolute errors (MAE), median absolute errors (MedAE), and the percentage of prediction errors (PEs) within +/- 0.25 D, +/- 0.50 D, +/- 1.00 D were analyzed. Results The Kane formula had the smallest MAE (0.43 D) and MedAE (0.34 D). The highest percentage of PE within +/- 0.25 D was for EVO 2.0 (37.91%) and the Holladay 1(NP-modified-W/K) formulas (37.91%). The Kane formula had the highest percentage of PEs in the range of +/- 0.50, +/- 0.75, +/- 1.00, and +/- 2.00 D. There was no significant difference in PEs within +/- 0.25, +/- 0.50 +/- 0.75 and +/- 1.00 D between BUII, Kane, EVO 2.0 and Wang-Koch AL adjusted formulas (P > .05) by using Cochran's Q test. The Holladay 2(modified-W/K) formula has the lowest percentage of hyperopic outcomes (29.38%). Conclusions The BUII, Kane, EVO 2.0 and Wang-Koch AL adjusted formulas have comparable accuracy for IOL power calculation in eyes with ALs > 30.0 mm.