PURPOSE: To compare the accuracy of a thick-lens intraocular lens (IOL) power formula using the manufacturer's cutting-card information (the Næser 1 formula) and calculated data from open sources (the Næser 2 formula) for IOL architecture; and to compare these results with the achievements of the Barrett Universal II, Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. SETTING: IRCCS GB Bietti Foundation, Rome, Italy. DESIGN: Retrospective case series. METHODS: For each IOL power formula, the prediction error in refraction was retrospectively calculated in eyes after phacoemulsification with implantation of the SN60WF posterior chamber IOL. The predictions made using the different formulas were optimized in retrospect by adjusting the respective constants. The mean arithmetic error (ME), the variance, and the median absolute error (MedAE) were calculated, as well as the dependency of the arithmetic error on the axial length. RESULTS: The study comprised 151 eyes. The Næser 1 and Næser 2 formulas were identical clinically and statistically. The ME (P = .278 with a one-way analysis of variance) and the variances for arithmetic errors (P = .248 with Levene's homogeneity test) were similar for all 7 formulas. A combined metric of ME, variance, MedAE, and arithmetic error on the axial length suggested the Næser 2 formula as the most accurate, followed by the Næser 1, Barrett Universal II, Haigis, SRK/T, Hoffer Q, and Holladay 1 formulas. CONCLUSIONS: The Næser thick-lens IOL power equations based on calculated and manufacturer's IOL data provided similar accuracies and performed approximately as the best thin-lens formulas. Cutting-card information is not necessary in current IOL power calculation.
PURPOSE: To compare the accuracy of a thick-lens intraocular lens (IOL) power formula using the manufacturer's cutting-card information (the Næser 1 formula) and calculated data from open sources (the Næser 2 formula) for IOL architecture; and to compare these results with the achievements of the Barrett Universal II, Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. SETTING: IRCCS GB Bietti Foundation, Rome, Italy. DESIGN: Retrospective case series. METHODS: For each IOL power formula, the prediction error in refraction was retrospectively calculated in eyes after phacoemulsification with implantation of the SN60WF posterior chamber IOL. The predictions made using the different formulas were optimized in retrospect by adjusting the respective constants. The mean arithmetic error (ME), the variance, and the median absolute error (MedAE) were calculated, as well as the dependency of the arithmetic error on the axial length. RESULTS: The study comprised 151 eyes. The Næser 1 and Næser 2 formulas were identical clinically and statistically. The ME (P = .278 with a one-way analysis of variance) and the variances for arithmetic errors (P = .248 with Levene's homogeneity test) were similar for all 7 formulas. A combined metric of ME, variance, MedAE, and arithmetic error on the axial length suggested the Næser 2 formula as the most accurate, followed by the Næser 1, Barrett Universal II, Haigis, SRK/T, Hoffer Q, and Holladay 1 formulas. CONCLUSIONS: The Næser thick-lens IOL power equations based on calculated and manufacturer's IOL data provided similar accuracies and performed approximately as the best thin-lens formulas. Cutting-card information is not necessary in current IOL power calculation.