Repeatability Data and Agreement of Keratometry With the VERION System Compared to the IOLMaster

Abstract

he exact measurement of the radius of the curvature of the cornea is crucial for planning the diopter of the intraocular lenses (IOLs) for implantation during cataract surgery. The error in measurements of the keratometric data can lead to unwanted postoperative refractive error. Although keratometric mistakes are not the first or most frequent source of error in today's biometric methods, 1 keratometry has an undisputed and important role in cataract surgery. Moreover, cases of implantation of toric IOLs require more precise keratometric readings and cylinder axis determination than ever before.There are numerous papers showing that the repeatability of keratometric measurements is excellent in the case of the IOLMaster (Carl Zeiss Meditec, Jena, Germany), 2-4 although above 42.0 diopters (D), the cylinder axis has relatively low repeatability data.2 In the case of the Lenstar (Haag-Streit, Koeniz, Switzerland), the interclass coefficient of the variation of the astigmatism axis was 0.915 and the mean arithmetic difference between the two measurement sessions was 3.19°, with an absolute difference of a median of 9°. 5 The Lenstar keratometry has repeatable values, 6,7 but according to Zhao et al., 7 the Lenstar and the IOLMaster cannot be used interchangeably in relation to keratometric data. With regard to average keratometric data, it seems that the Lenstar is biometrically equivalent to the IOLMaster, 8 and the correlation between the cylinder axis measurements of the IOLMaster and the Lenstar is high.9 However, Rohrer et al. 9 observed that the differences between the axis value of the flattest meridian in the Lenstar and the IOLMaster in a large percentage of patients is unacceptably high. Besides these controversialTo analyze the repeatability of keratometric and white-to-white (WTW) distance measurements with the VERION Measurement Module (Alcon Laboratories, Inc., Fort Worth, TX) and to compare the measured data to the results of the IOLMaster (Carl Zeiss Meditec, Jena, Germany). METHODS:Three images were captured with the VERION and the flattest and steepest keratometric data, the astigmatism axis, and the WTW distance were recorded. Subsequently, the axial length, the keratometric data with axis, and the WTW distance were measured with an IOLMaster. The repeatability data of the keratometric value of the VERION System, converted to cross cylinder J 0 and J 45 vector components, were analyzed. The agreement data for keratometry obtained by the VERION System and the differences regarding keratometric data and WTW distance compared to IOLMaster were calculated. RESULTS:The measurements were conducted in 50 eyes of 50 healthy volunteers (median age: 50.32 years, range: 19.34 to 85.3 years). The flattest and the steepest keratometric data, the diopter of astigmatism, the J 0 and J 45 vector components, and WTW distance did not differ significantly between devices (P > .05). Intraclass correlation coefficients (range: 0.863 to 0.994) and Cronbach's alpha values (range: 0.950 to 0.998) were high for all p...

Comparison of corneal power obtained from VERION image-guided surgery system and four other devices

“…They found that the SMI Reference Unit, LenStar, and IOL master devices all had comparable reliability in providing accurate K-values measurements. Additionally, Nemeth et al27 reported that VERION has high repeatability and agreement with the IOL master.…”

Comparison of keratometric measurements obtained by the Verion Image Guided System with optical biometry and auto-keratorefractometer

“…The Verion Image Guided System has been shown to have high repeatability [4], and recently it has also been shown that, its use resulted in less postoperative deviation from target-induced astigmatism and showed less postoperative toric IOL misalignment than using a manual-marking technique [5]. Therefore, it is a candidate to have an increasing role in cataract surgery planning, especially in toric IOL patients and for limbal relaxing incisions.…”

“…Up to date, there is only one study which analyzed the repeatability of keratometric and white-to-white distance measurements with the Verion Measurement Module in 50 eyes of 50 healthy volunteers [4]. The measurements were also compared with the IOLMaster in the same study.…”

Validation of keratometric measurements obtained with an intraoperative image‐guided system: intra‐session repeatability and interchangeability with an optical biometer

“…We estimated the number of pairs needed to detect a true difference in population means (δ) with type I error probability α given a standard deviation (σ). Specifically, for a statistical power of 80 per cent, considering δ and σ reported comparing the Verion system and the optical biometer system IOLMaster, and an α error of 0.05, the sample size required was 53 eyes.…”

“…To our knowledge, only one study to date has evaluated the intra‐session repeatability of keratometric astigmatism obtained with the Verion System (Alcon Laboratories Inc., Fort Worth, Texas, USA), with an analysis of the interchangeability of such measurement with that provided by the IOLMaster optical biometer. The aim of our study was to evaluate in healthy eyes the intra‐session repeatability of point‐based keratometric readings and astigmatism value obtained with the Verion system.…”