To compare the accuracy of the Barrett True-K formula with other methods available on the American Society of Cataract and Refractive Surgery (ASCRS) post-refractive surgery intraocular lens (IOL) power calculator for the prediction of IOL power after previous myopic laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and private practice, Mesa, Arizona, USA. Retrospective case series. The accuracy of the Barrett True-K formula was compared with the Adjusted Atlas (4.0 mm zone), Masket, modified-Masket, Wang-Koch-Maloney, Shammas, and Haigis-L methods to calculate IOL power. A separate analysis of 2 no-history methods (Shammas and Haigis-L) was performed and compared with the Barrett True-K no-history option. Eighty-eight eyes were available for analysis. The Barrett True-K formula had a significantly smaller median absolute refraction prediction error than all other formulas except the Masket, smaller variances compared with the Wang-Koch-Maloney, Shammas, and Haigis-L, and a greater percentage of eyes within ±0.50 diopter (D) of predicted error in refraction compared with the Adjusted Atlas, Masket, and modified Masket methods (all P < .05). In eyes with no historical data, the Barrett True-K no-history formula had a significantly smaller median absolute refraction prediction error and a greater percentage of eyes within ±0.50 D of the predicted error in refraction than the Shammas and the Haigis-L formulas (both P < .05). The Barrett True-K formula was either equal to or better than alternative methods available on the ASCRS online calculator for predicting IOL power in eyes with previous myopic LASIK or PRK.

To evaluate and compare the accuracy of formulas and methods for calculating the intraocular lens (IOL) power for eyes with an axial length (AL) greater than 26.0 mm. Ein-Tal Eye Center, Tel-Aviv, Israel. Retrospective case series. The postoperative refraction results in myopic eyes with an AL over 26.0 mm were compared with the predicted refractions calculated using standard formulas (Holladay 1, SRK/T, Hoffer Q, and Haigis) with optical IOL constants, User Group for Laser Interference Biometry constants, and an AL-adjustment method and using new-generation formulas (Barrett Universal II, Holladay 2, and Olsen). In 76 (71.7%) of 106 eyes, the IOL was 6.0 diopters (D) or more (Group A) and in 30 eyes (28.3%) was less than 6.0 D (Group B). In Group A, the SRK/T, Hoffer Q, Haigis, Barrett Universal II, Holladay 2, and Olsen methods met the benchmark criteria of having a prediction error of ±0.5 D in at least 71.0% of eyes and ±1.0 D in 93.0% of eyes. In Group B, only the Barrett Universal II formula and the Holladay 1 and Haigis formulas using the AL-adjusted method met those criteria. When selecting IOLs for high and extreme myopia, choosing appropriate formulas and methods can yield accurate refractive results that meet benchmark criteria. No author has a financial or proprietary interest in any material or method mentioned.

To evaluate and compare the accuracy of 2 toric intraocular lens (IOL) calculators with or without a new regression formula. Ein-Tal Eye Center, Tel-Aviv, Israel, and the Lions Eye Institute, Nedlands, Western Australia, Australia. Retrospective case series. A new regression formula (Abulafia-Koch) was developed to calculate the estimated total corneal astigmatism based on standard keratometry measurements. The error in the predicted residual astigmatism was calculated by the Alcon and Holladay toric IOL calculators with and without adjustments by the Abulafia-Koch formula. These results were compared with those of the Barrett toric calculator. Data from 78 eyes were evaluated to validate the Abulafia-Koch formula. The centroid errors in predicted residual astigmatism were against-the-rule with the Alcon (0.55 diopter [D]) and Holladay (0.54 D) toric calculators and decreased to 0.05 D (P < .001 [x-axis], P = .776 [y-axis]) and 0.04 D (P < .001 [x-axis], P = .726 [y-axis]) with adjustments by the Abulafia-Koch formula. The Alcon and the Holladay toric calculators had a higher proportion of eyes within ±0.50 D of the predicted residual astigmatism with the Abulafia-Koch formula (76.9% and 78.2%, respectively) than without it (both 30.8%). There were no significant differences between the results of the Abulafia-Koch-modified Alcon and the Holladay toric calculators and those of the Barrett toric calculator. Adjustment of commercial toric IOL calculators by the Abulafia-Koch formula significantly improved the prediction of postoperative astigmatic outcome. Dr. Abulafia received a speaker's fee from Haag-Streit AG. Dr. Barrett has licensed the Barrett Toric Calculator to Haag-Streit AG. Dr. Koch is a consultant to Alcon Laboratories, Inc., Abbott Medical Optics, Inc., and Revision Optics, Inc. Dr. Hill is a paid consultant to Haag-Streit AG and Alcon Laboratories, Inc. None of the other authors has a financial or proprietary interest in any material or method mentioned.

To evaluate and compare the accuracy of different methods to measure and predict postoperative astigmatism with toric intraocular lens (IOL) implantation. Ein-Tal Ophthalmology Center, Tel-Aviv, Israel. Retrospective case series. Postoperative corneal astigmatism was measured with 3 devices (IOLMaster 500; optical low-coherence reflectometry [OLCR]-based Lenstar LS 900; Atlas topographer) and compared with the manifest astigmatic refractive outcome in patients with toric IOLs. The error in the predicted residual astigmatism was calculated by vector analysis according to the measurement and calculation method used to predict the required toric IOL cylinder power. The centroid errors in predicted residual astigmatism were against the rule with the Alcon and Holladay toric calculators (0.53 to 0.56 diopter [D]), were lower with the Baylor nomogram (0.21 to 0.26 D), and were lowest for the Barrett toric calculator (0.01 to 0.16 D) (P <.001). The Barrett toric calculator had the lowest median absolute error in predicted residual astigmatism (0.35 to 0.54 D, all devices) compared with the Alcon and Holladay toric calculators with or without the Baylor nomogram (P <.021). The Barrett toric calculator and the OLCR device achieved the most accurate results; 75.0% and 97.1% of eyes were within ±0.50 D and ±0.75 D of the predicted residual astigmatism, respectively. Prediction of astigmatic outcomes with toric IOLs can be improved with appropriate measuring devices and methods to establish the required toric IOL power.

PURPOSE: To evaluate and compare the accuracy of three toric intraocular lens (IOL) calculators using keratometry measurements derived from the anterior corneal curvature and direct measurements of the posterior corneal curvature. METHODS: Postoperative corneal astigmatism was measured by the IOLMaster (Carl Zeiss Meditec, Jena, Germany) and Pentacam (Oculus Optikgeräte, Wetzlar, Germany). The data were processed by the Alcon, Holladay, and Barrett toric IOL calculators. The error in predicted residual astigmatism (PredRA) was calculated by subtracting the PredRA from the postoperative subjective refraction by vector analysis. RESULTS: The centroid errors in PredRA were against-the-rule (ATR) with the Alcon (0.56 diopters [D]) and Holladay (0.55 D) toric calculators using the IOLMaster (Carl Zeiss Meditec, Jena, Germany) measurements. The centroid errors in PredRA were lower when Pentacam (Oculus Optikgeräte, Wetzlar, Germany) measurements were used (0.38 D, ATR). The Barrett toric calculator using the IOLMaster measurements had the lowest centroid errors in PredRA (0.02 D, P < .001) and achieved the most accurate results: 75.8% and 92.9% of eyes were within 0.50 and 0.75 D of the PredRA, respectively. CONCLUSIONS: The prediction of the postoperative astigmatic outcome can be improved by using appropriate methods of adjustment for posterior corneal astigmatism. [ J Refract Surg. 2015;31(10):699–706.]

Purpose: To evaluate the accuracy of the Hill-RBF 3 formula, with and without direct measurements of total corneal power, using a heteroscedastic statistical method for analysis. Setting: Department of Ophthalmology, Shaare Zedek Medical Center, Jerusalem, Israel. Design: Retrospective, consecutive case series. Methods: Records of consecutive patients who underwent routine cataract surgery between February 2018 and June 2020 were retrospectively reviewed. The prediction accuracy of the Hill-RBF 3.0 formula was compared with that of the Barrett Universal II, Emmetropia Verifying Optical 2.0, Haigis, Hill-RBF 2.0, Hoffer Q, Holladay 1, Holladay 2, Kane, Olsen, and SRK/T formulas, based on biometry measurements by swept-source optical coherence tomography (SS-OCT) with standard keratometry (K), SS-OCT with total keratometry (TK), and an optical low-coherence reflectometer (OLCR). Statistical analysis was applied according to a heteroscedastic statistical method with SD of prediction errors as the main parameter for formula performance. Results: The study included 153 eyes of 153 patients. The SD values that were obtained by Hill-RBF 3.0 (0.266 to 0.285 diopters [D]) were significantly lower compared with those by Hill-RBF 2.0 (0.290 to 0.309 D), Hoffer Q (0.387 to 0.407 D), Holladay 1 (0.367 to 0.385 D), Holladay 2 (0.386 to 0.401 D), and SRK/T (0.377 to 0.399 D) formulas (P < .036). The prediction accuracy of the Hill-RBF 3.0 was similar across the SS-OCT (K), SS-OCT (TK), and OLCR methods of measurement (P > .51). Conclusions: The Hill-RBF 3.0 was more accurate than the Hill-RBF 2.0 and older generation formulas and had similar prediction accuracy compared with new generation formulas. The use of TK did not provide significant improvement to its prediction accuracy.