Comparison of 9 intraocular lens power calculation formulas

PURPOSE: To evaluate the accuracy of 9 intraocular lens (IOL) calculation formulas using 2 optical biometers. SETTING: Private practice, Saint Joseph, Michigan, USA. DESIGN: Retrospective consecutive case series. METHODS: Nine IOL power formula predictions with observed refractions after cataract surgery were compared using 1 IOL platform. The performance of each formula was ranked for accuracy by machine and by axial length (AL). The Olsen was further divided by a preinstalled version (Olsen(OLCR)) and a purchased version (Olsen(Standalone)). The Holladay 2 was divided by whether a refraction was entered (Holladay 2(PreSurgRef)) or not (Holladay 2(NoRef)). The OLCR device used in the study was the Lenstar L5 900 and the PCI device, the IOLMaster. RESULTS: The formulas were ranked by the standard deviation of the prediction error (optical low coherence reflectometry [OLCR], partial coherence interferometry [PCI]) as follows: Olsen(Standalone) (0.361, 0.446), Barrett Universal II (0.365, 0.387), Olsen(OLCR) (0.378, not applicable), Haigis (0.393, 0.401), T2 (0.397, 0.404), Super Formula (0.403, 0.410), Holladay 2(NoRef) (0.404, 0.417), Holladay 1 (0.408, 0.414), Holladay 2(PreSurgRef) (0.423, 0.432), Hoffer Q (0.428, 0.432), and SRK/T (0.433, 0.44). CONCLUSIONS: The formulas gave different results depending on which machine measurements were used. The Olsen formula was the most accurate with OLCR measurements, significantly better than the best formula with PCI measurements. The Olsen was better, regardless of AL. If only PCI measurements (without lens thickness) were available, the Barrett Universal II performed the best and the Olsen formula performed the worst. The preinstalled version of Olsen was not as good as the standalone version. The Holladay 2 formula performed better when the preoperative refraction was excluded.