Assessing the interchangeability of keratometry measurements from four biometric devices in intraocular lens power calculations: insights into the predictive accuracy of five modern IOL formulas

Abstract

Background: Achieving accurate intraocular lens (IOL) power calculation is crucial for successful refractive outcomes in cataract surgery. This study aimed to evaluate the interchangeability of keratometry (K) values obtained from four biometric devices (IOLMaster 700, CASIA2, Pentacam, and iTrace) and assess the predictive accuracy of five modern IOL calculation formulas (Barrett Universal II, Cooke K6, EVO 2.0, Kane, and PEARL-DGS) when using K values from these different devices.

Methods: This prospective study included K values obtained from four biometric devices for use in five IOL power calculation formulas. Predictive accuracy was assessed using multiple statistical parameters, including standard deviation (SD), mean absolute error (MAE), median absolute error (MedAE) and root mean square absolute error (RMSAE). The interchangeability of devices was evaluated by comparing predictive outcomes across devices and formulas, with statistical analyses focusing on consistency and agreement.

Results: Predictive accuracy across the five IOL formulas was stable and showed no statistically significant differences when using keratometry measurements from the same biometric device. However, significant variability was noted when comparing K values from different devices using the same formula. The SS-OCT-based devices (IOLMaster 700 and CASIA2) showed higher consistency in predictive accuracy compared to Scheimpflug-based Pentacam and ray-tracing-based iTrace. Despite this inter-device variability, all five IOL formulas showed overall robust performance across different devices.

Conclusions: Our findings indicate that keratometry measurements from different biometric devices are not fully interchangeable. SS-OCT-based devices (IOLMaster 700 and CASIA2) provided superior consistency in refractive prediction accuracy. Therefore, clinicians should carefully select biometric device-formula combinations based on the specific measurement principles and desired refractive outcomes. Further research involving larger sample sizes, additional IOL types and biometric devices, as well as assessment of surgeon-related factors, is warranted to optimize refractive accuracy in cataract surgery.

Keywords: Biometric devices; Cataract surgery; IOL power calculation; Keratometry values; Refractive outcomes.

Fig. 1

Standard cataract surgery outcome analysis. (a) Postoperative uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA). (b) Histogram of the lines of difference between postoperative UDVA and CDVA. (c) Postoperative spherical equivalent (SEQ) outcomes. (d) Residual refractive cylinder outcomes

Fig. 2

Comparative analysis of biometric devices and formulas. (a) Bar chart comparing Kf, Ks, and Km values across four devices. (b) Bar chart showing standard deviation (SD) values for five formulas across four devices. (c). Bar chart comparing mean absolute error (MAE) for five formulas across four devices. (d) Bar chart illustrating median absolute error (MedAE) for five formulas across four devices. (e) Violin plot showing absolute prediction error (APE) distributions for each device-formula combination. Note: Statistically significant difference at *p-values < 0.05; **p-value < 0.01

Fig. 3

Refractive error prediction accuracy across devices and formulas description. (a) Stacked bar graph showing percentage distribution of eyes within refractive error ranges for five formulas across four devices. (b) Stacked bar graph comparing refractive error ranges for each device across the five formulas

Fig. 4

Bland-Altman comparison of refractive prediction errors between biometric devices. (a) IOLMaster 700 vs. CASIA2, with subplots a1-a5 showing comparisons for the five formulas. (b) IOLMaster 700 vs. Pentacam, with subplots b1-b5 for each formula. (c) IOLMaster 700 vs. iTrace, subplots c1-c5 showing comparisons across formulas. (d) CASIA2 vs. Pentacam, subplots d1-d5 for each formula. (e) CASIA2 vs. iTrace, subplots e1-e5 for formula comparisons. (f) Pentacam vs. iTrace, subplots f1-f5 showing comparisons for each formula. Each plot illustrates the agreement and variation between the devices, with 95% limits of agreement and mean differences highlighted. BII, Barrett Universal II; K6, Cooke K6; EVO, emmetropia verifying optical; DGS, Pearl-DGS