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Agreement between the Topolyzer Vario and Oculyzer II for corneal keratometry, asphericity, and Fourier analysis

Poster Details

First Author: F.Faria Correia PORTUGAL

Co Author(s):    S. Ribeiro   T. Monteiro   R. Ambrosio Jr              

Abstract Details


To evaluate inter-device agreement between Placido topography (Topolyzer Vario, Erlangen, Wavelight) and Scheimpflug tomography (Oculyzer II; Wavelight, Erlangen, Germany) for measuring keratometry, cylinder and axis of astigmatism, asphericity, decentration and irregularity based on Fourier analysis.


CUF Porto


Observational case series of 50 eyes randomly selected from 50 candidates for laser vision correction. Main outcome measures were keratometry (K1 and K2 readings), cylinder and axis of astigmatism, asphericity (Q value), decentration (magnitude and axis) and irregularity based on Fourier analysis and their agreement was evaluated by Bland–Altman analysis.


For the selected parameters, there were no statistical differences between both devices (paired t-test; p < 0.05). The parameters K1, K2, cylinder and axis of astigmatism obtained high levels of correlation coefficients between both devices and the 95% limits of agreement (LoA) were considered good (except the K2 parameter: -0.54 to 0.65). In contrast, the Q value, decentration and irregularity variables presented a good correlation coefficient (Pearson correlation of 0.736, 0.579 and 0.545; respectively; p < 0.05). The 95% LoA of the Q value was -0.12 to 0.12, decentration magnitude was -0.12 to 0.11 and irregularity was -0.008 to 0.009.


Except for the K2 variable, Placido topography and Scheimpflug tomography show good agreement for the data for the keratometry readings, and these devices could be used interchangeably. Despite the less correlation presented by the Fourier Analysis, the parameters displayed good LoA, but caution should be taken when used interchangeably.

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