December 30, 2025
2 min read
Key takeaways:
- Ray tracing provided no advantage over available IOL calculators.
- The ESCRS calculator provided similarly positive results.
Different IOL calculators provided similar results in patients with a history of LASIK surgery, according to a study published in the Journal of Refractive Surgery.
Thomas Kohnen, MD, PhD, and colleagues wrote that corneal refractive surgery has been shown to complicate the accuracy of IOL power calculations because the surgery alters the relationship between the anterior and posterior corneal refractive power.
Ray tracing showed no advantage over available IOL calculators in a recent study. Image: Adobe Stock
“Formulas that predict the exact lens position from the corneal curvature are known to be inaccurate when corneal curvature and refractive power are altered by refractive surgery,” they wrote. “Accurate calculation of IOL power is particularly important because patients have high expectations after cataract surgery with modern IOLs and often wish for spectacle independence for most daily activities, for example by implanting an extended depth of focus (EDOF) or multifocal IOL.”
Researchers conducted a consecutive case series of 34 eyes from 34 patients who underwent implantation with a non-diffractive EDOF IOL after myopic LASIK. They collected preoperative assessments, including biometry and tomography, using Scheimpflug technology (Pentacam, Oculus).
They compared seven IOL calculation formulas designed for use after myopic LASIK, which included:
Potvin-Hill-Shammas-PM;
Okulix ray tracing;
PEARL-DGS;
PEARL-DGS with posterior radial curvature;
Barrett True-K no history with measured and predicted posterior corneal astigmatism;
Hoffer QST; and
EVO 2.0.
They also used the European Society of Cataract and Refractive Surgery online calculator for three formulas.
Kohnen and colleagues found high trueness for all formulas except for ray tracing (-0.4 ± 0.6; P < .01). There were no significant differences in accuracy. Researchers found that more than 59% of eyes were within 0.5 D, and more than 85% were within 1 D for all formulas, according to the study.
When using the recommended IOL constraints or constants from the IOL Con database, researchers found similar results for all formulas included in the ESCRS calculator.
“The use of biometric and tomographic data measured by Scheimpflug technology for the calculation of IOL power in eyes that have previously undergone myopic LASIK surgery has yielded favorable outcomes when employing the recommended IOL constants from a recognized database,” Kohnen and colleagues wrote. “In the current study, the employment of ray tracing technique did not demonstrate a significant advantage over alternative, more recent calculation formulas, both with and without the measurement of the posterior corneal surface.”
Sources/Disclosures
Source:
Kohnen T, et al. J Refract Surg. 2025;doi:10.3928/1081597X-20250707-07.
Disclosures:
Kohnen reports being a consultant, researcher and lecturer for Alcon, Oculus, Schwind eye-tech-solutions and STAAR Surgical; a consultant and lecturer for Tarsus and Ziemer; a researcher and lecturer for Teleon Surgical; a consultant for AbbVie, Geuder, LensGen, Santen, Stadapharm, Thieme and Zeiss; and a lecturer for Allergan, Bausch + Lomb, Johnson & Johnson, Medupdate and Streamed Up. See the full study for all other authors’ relevant financial disclosures.
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