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Comparison of Prediction Accuracy of Six Toric IOL Power Calculation Formulas, Including Four Available on the ESCRS
Francisco J Castro-Alonso1,2,3, Rubén Hernández Vián1,2,3, Marta Jiménez-García1,2,4
1GIMSO Department of Ophthalmology, Institute for Health Research Aragón, University Hospital Miguel Servet, Zaragoza, Spain.
Purpose:
To evaluate and compare the prediction accuracy of toric IOL power calculation formulas available on the ESCRS online calculator, the Abulafia-Koch combined with Hill-RBF and Castrop formulae, and assess their effectiveness in predicting actual postoperative refractive outcomes.
Patients And Methods:
The preoperative and 4-5 week postoperative records of 131 patients who underwent phacoemulsification and implantation of enVista toric (MX60T) IOL were reviewed retrospectively. The IOL power calculation formulas available on the ESCRS online calculator (Kane, EVO, Hoffer QST, and Barrett), Abulafia-Koch combined with Hill-RBF and Castrop formulae, were used to obtain predicted postoperative refraction for the implanted IOL. Spherical equivalent and residual astigmatism prediction errors (SEQ-PE and RA-PE) were compared statistically using Eyetemis. Results were expressed as trueness, accuracy, and precision.
Results:
Mean corneal astigmatism decreased from 2.47±0.95 D preoperatively to 0.34±0.28 D postoperatively; 88.6% of eyes achieved cylinder ≤0.50 D. For SEQ-PE, trueness was comparable for Abulafia-Koch combined with Hill-RBF, Castrop, EVO, and Barrett, with trimmed means ranging between -0.02 to 0.02 D. Precision was similar for EVO, Kane, and Barrett (0.16-0.18 D) and lower for Abulafia-Koch combined with Hill-RBF and Hoffer QST formulas. Accuracy was comparable among Barrett, Castrop, EVO, and Kane, with Barrett, EVO, and Kane formulas achieving the highest proportion of eyes (>93%) within ±0.50 D of prediction error. For RA-PE, the trueness and precision of Abulafia-Koch combined with Hill-RBF, Hoffer QST, EVO, Kane, and Barrett formulas were high and comparable. Trueness ranged from 0.08 to 0.14 D and precision from 0.34 D to 0.37 D. All formulas except Castrop showed good astigmatic prediction accuracy, with more than two-thirds of eyes achieving absolute RA-PE within 0.50 D.
Conclusion:
Among the evaluated formulas, the EVO, Barrett, and Kane formulas showed high refractive and astigmatic predictability, supporting their reliability for toric IOL power calculation.