Biometry measurement errors or eyes with deviations in average biometry can cause inaccurate power calculation during cataract surgery. A novel intraocular lens power calculation method has been found to enhance accuracy.
Patients can achieve improved vision parameters after cataract surgery when the power of their implanted intraocular lens (IOL) is calculated correctly. “Even if an optical biometer improves the accuracy and reproducibility of a measurement, errors due to the measurement method itself can occur,” researchers noted in a study published in Scientific Reports. Errors in the power calculation formula that predicts the most effective lens position are also a factor in lens accuracy.
Researchers analyzed data from 1,600 eyes of 1,600 patients who underwent phacoemulsification and in-the-bag implantation of a ZCB00 IOL. These patients were divided into 2 groups: a reference dataset of 1,200 eyes that was further divided into 768 biometric subgroups based on axial length, keratometry, and anterior chamber depth and used to develop the new IOL power calculator, and a validation dataset of 400 eyes to assess its accuracy.
Four existing power calculation formulas were used to compare preoperative predicted refraction with postoperative spherical equivalent refraction. The formula that provided the smallest difference was selected to be used in the biometric subgroups of the Eom power selection method. The study then compared the median absolute errors (MedAEs) and IOL Formula Performance Indexes (FPIs) of several IOL power calculation formulas with the newly developed Eom formula.
The MedAE of the Eom formula was 0.22 diopters (D), which was significantly smaller than those of other formulas. The Eom formula also showed the highest IOL FPI of 0.553, indicating superior performance compared to the other formulas. It performed particularly well in eyes with axial lengths between 22.0 mm and 25.0 mm, showing a MedAE of 0.23 D, which was lower than most other formulas. In eyes with short axial lengths (<22.0 mm), the Eom formula's performance was comparable to the best-performing formulas, and in eyes with long axial lengths (>25.0 mm), the Eom formula showed a significant improvement in accuracy of 20 D compared with another formula.
“Traditional optical biometers use a single refractive index for measuring axial length, and this could be a reason for unexpected refractive errors after cataract extractions,” the researchers noted. Using an amalgamation of existing formulas helps to leverage the strengths of each method for improved IOL power prediction accuracy with the Eom formula.
A full list of author disclosures can be found in the published research
