Abstract
Purpose: 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. Methods: 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. Results: 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. Conclusion: 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.
Highlights
Standard and total keratometric readings obtained with the intraocular lens (IOL)-Master system were significantly higher than those obtained with the other two devices (p≤0.003)
This is consistent with the results of a previous comparative study of keratometric measurements provided by the IOL-Master 500, Cassini, and Pentacam systems [26]
It should be considered that keratometry is calculated for a 3-mm area with the Pentacam and Cassini topography systems, whereas calculations with the IOL-Master system are performed for a 2.5-mm optical zone
Summary
The magnitude of posterior corneal astigmatism (PCA) has been demonstrated to be correlated with anterior corneal astigmatism (ACA) for patients with with-the-rule (WTR) astigmatism, but there was a weak and no correlation for oblique and against-the-rule (ATR) eyes, respectively [6]. Different algorithms of correction of keratometric estimations of total corneal astigmatism have been developed to consider the potential contribution of PCA to the calculations of the power of toric IOLs, as well as the contribution of incision-induced posterior corneal astigmatism and effective lens position [3, 8 - 12]. Comparative studies are necessary to evaluate the level of interchangeability of all these measures and how differences among estimations can influence the refractive correction predictability achievable with toric IOLs. The aim of the current study was 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
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