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. 2019 Mar 18;12(3):412-416.
doi: 10.18240/ijo.2019.03.10. eCollection 2019.

Interchangeability of corneal curvature and asphericity measurements provided by three different devices

David P Piñero  1   2 , Roberto Soto-Negro  2 , Pedro Ruiz-Fortes  2 , Rafael J Pérez-Cambrodí  2 , Hideki Fukumitsu  2   3
Affiliations

Interchangeability of corneal curvature and asphericity measurements provided by three different devices

David P Piñero et al. Int J Ophthalmol. .

Abstract

Aim: To evaluate the interchangeability of keratometric and asphericity measurements provided by three measurement systems based on different optical principles.

Methods: A total of 40 eyes of 40 patients with a mean age of 34.1y were included. In all cases, a corneal curvature analysis was performed with IOL-Master (IOLM), iDesign 2 (ID2), and Sirius systems (SIR). Differences between instruments for flattest (K1) and steepest (K2) keratometric readings, as well as for magnitude and axis of corneal astigmatism were analyzed. Likewise, differences in asphericity (Q) between SIR and ID2 were also evaluated.

Results: Mean differences between devices for K1 were 0.20±0.21 (P<0.001), -0.12±0.36 (P=0.046) and -0.32±0.36 D (P<0.001) for the comparisons IOLM-SIR, IOLM-ID2 and SIR-ID2, respectively. The ranges of agreement for these comparisons between instruments were 0.41, 0.70, and 0.70 D. For K2, mean differences were 0.31±0.33 (P<0.001), -0.08±0.43 (P=0.265) and -0.39±0.38 D (P<0.001), with ranges of agreement of 0.65, 0.84, and 0.74 D. Concerning magnitude of astigmatism, ranges of agreement were in the limit of clinical relevance (0.49 D, P=0.011; 0.55 D, P=0.386; 0.43 D, P=0.05). In contrast, ranges of agreement were clinically relevant for astigmatic axis (26.68°, 33.83° and 18.37°, P≥0.121) and for Q between SIR and ID2 (0.16, P<0.001).

Conclusion: The keratometric corneal power, astigmatic axis and asphericity measurements provide by the three systems evaluated cannot be considered as interchangeable, whereas measurements of corneal astigmatism obtained with SIR and ID2 can be considered as interchangeable for clinical purposes.

Keywords: astigmatism; corneal asphericity; corneal topography; keratometry.

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Figures

Figure 1
Figure 1. Bland-Altman plots for the comparison of the values of keratometric power in the flattest meridian (K1) obtained with SIR systems and iDesign 2 (ID2) systems
The dotted lines show the limits of agreement (±1.96SD).
Figure 2
Figure 2. Bland-Altman plots for the comparison of the values of keratometric power in the steepest meridian (K2) obtained with Sirius (SIR) and iDesign 2 (ID2) systems
The dotted lines show the limits of agreement (±1.96SD).
Figure 3
Figure 3. Bland-Altman plots for the comparison of the values of keratometric astigmatism (AST) obtained with Sirius (SIR) and iDesign 2 (ID2) systems
The dotted lines show the limits of agreement (±1.96SD).
Figure 4
Figure 4. Bland-Altman plots for the comparison of the values of the orientation (axis) corresponding to the flattest meridian obtained with Sirius (SIR) and iDesign 2 (ID2) systems
The dotted lines show the limits of agreement (±1.96SD).
See this image and copyright information in PMC

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