Comparison of Standard and Total Keratometry Astigmatism Measured with three Different Technologies

Humberto Carreras1, *, Ángel G. García1, David P Piñero2, 3, *
1 Vithas Eurocanarias Instituto Oftalmológico, Las Palmas de Gran Canarias, Spain
2 Department of Ophthalmology. Vithas Medimar International Hospital, Alicante, Spain
3 Department of Optics, Pharmacology and Anatomy, University of Alicante, Spain

© 2020 Carreras et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to these authors at Vithas Eurocanarias Instituto Oftalmológico, C/ León y Castillo 211-35004 Las Palmas de Gran Canaria, Spain; Tel: (+34) 928 49 10 90; E-mail: and Department of Optics, Pharmacology and Anatomy, University of Alicante, Crta San Vicente del Raspeig s/n, 03690 San Vicente del Raspeig, Alicante, Spain; Tel: +34 965 903400; E-mail:



To compare the keratometric and total corneal astigmatism measures provided by three different technologies as well as to assess the level of interchangeability among them.


A Prospective, comparative study enrolling 94 eyes from 53 patients (age, 29-77 years) was carried out. All participants were patients with the diagnosis of cataract or patients with a transparent crystalline lens but seeking surgical presbyopia correction. A complete eye examination was performed in all eyes, including corneal analysis with three different devices: IOL-Master 700 (Carl Zeiss Meditec), Cassini (i-Optics), and Pentacam (Oculus Optikgeräte GmbH). Interchangeability of standard and total keratometric readings (equivalent keratometric readings for Pentacam) and astigmatism measures with these three systems were evaluated with the Bland-Altman analysis.


Significantly higher standard and total keratometric readings were obtained with the IOL-Master compared to the other two systems (p<0.001). Likewise, a significantly higher magnitude of standard and total keratometric astigmatism was obtained with the Cassini system (p<0.001). Ranges of the agreement for corneal power measurements between devices varied from 0.58 D to 1.53 D, whereas they ranged from 0.46 D to 1.37 D for standard and total astigmatism measurements.


Corneal power and astigmatism measures obtained with IOL-Master 700, Cassini, and Pentacam systems cannot be used interchangeably. The impact of these differences on the refractive predictability achieved with different types of intraocular lenses (IOL) should be evaluated in the future in order to define which is the best corneal evaluation approach for optimizing the IOL power calculations.

Keywords: Corneal topography, Color light-emitting diode reflection topography, Pentacam, Scheimpflug imaging, IOL-Master, Optical biometry, Keratometry.