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Correlation between the dioptric power, astigmatism and surface shape of the anterior and posterior corneal surfaces

By David Mas, Julián Espinosa Tomás, Begoña Domenech, Jorge Pérez Rodríguez, Henryk T. Kasprzak and Carlos Illueca Contri

Abstract

A knowledge of the shape of the cornea is of major importance for the planning and monitoring of surgery, and for the correct diagnosis of corneal diseases. Many authors have studied the geometry of the second corneal surface in the central region and it has been stated that there is a high correlation between the central radii of curvature and asphericities of the two corneal surfaces. In this work we extend this study to a larger, central, 6 mm diameter of the cornea. Surface height data, obtained with an Oculus Pentacam from 42 eyes of 21 subjects, were analysed to yield surface power vectors. Corneal heights of both surfaces were also decomposed into low order Zernike polynomials and the correlations between each of the power vectors and low-order Zernike coefficients for the two surfaces were studied. There was not only a strong correlation between spherical powers and Zernike defocus coefficients, but also between the astigmatic components. The correspondence between the astigmatism in both surfaces found here can be of the utmost importance in planning optical surgery, since perfect spherical ablation of the first surface does not assure total correction of corneal astigmatism.This work has been partially supported by the Spanish Ministry of Education and Science through the project nr. FIS2005-05053. Julian Espinosa and Jorge Perez acknowledge financial support from the University of Alicante through the project GRE07-7P. Henryk Kasprzak acknowledges the University of Alicante for its economical support through the project Senior 08/07

Topics: Cornea, Pachymetry, Scheimpflug camera, Zernike polynomials, Óptica
Publisher: Blackwell Publishing
Year: 2009
DOI identifier: 10.1111/j.1475-1313.2008.00632.x
OAI identifier: oai:rua.ua.es:10045/10418

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