Refractive Surgery/Vision Correction

New Ray-Tracing–Based IOL Power Calculation Shows Accuracy in Pilot Evaluation

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Intraocular lens (IOL) calculation formulas have significantly improved refractive results, but errors still exist. Optical ray tracing is a more promising concept of IOL power calculation and is more precise in corneal power calculation. The procedure uses exact Snell’s law, providing a real simulation of the human eye. A recent study in the Journal of Cataract and Refractive Surgery examined the spherical equivalent (SE) refractive prediction error of a new ray-tracing–based IOL power calculation and compared the outcomes with different IOL calculation formulas.

The theoretical prospective monocentric study was conducted at Hanusch Hospital, Vienna, Austria, and included 40 eyes of 40 patients who were scheduled for cataract surgery and implantation of a monofocal aspheric plate-haptic IOL. They were examined at 1-day, 1-week, and 1-month follow-up.

The ray-tracing–based IOL power calculation was performed using retinal image quality metrics criteria for IOL power selection. IOL power calculations were also made using Barrett Universal II, Hill-RBF, SRK/T, and Haigis formulas.

Statistical analysis results showed that absolute error of the ray-tracing–based IOL power calculation was lower compared with the SRK/T (P = 0.020) and Haigis (P = 0.029) formulas. In addition, the mean absolute error (MAE) in SE refraction was statistically significantly lower in the ray-tracing group (0.33 ± 0.29 D) compared with the Haigis group (0.41 ± 0.33 D).

The new ray-tracing–based IOL calculation is a promising tool for postoperative refraction outcomes and may help with IOL selection and managing patient expectations.


Hirnschall N, Buehren T, Trost M, Findl O. Pilot evaluation of refractive prediction errors associated with a new method forray-tracing–based intraocular lens power calculation. J Cataract Refract Surg. 2019; 45:738–744. doi:10.1016/j.jcrs.2019.01.023.

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