Quantitative assessment of videokeratography data using fourier series harmonic analysis.

PURPOSE: To describe a method of mathematically decomposing videokeratography data using Fourier series harmonic analysis and present examples of its clinical application.

METHODS

Videokeratography data were decomposed by Fourier analysis into spherical component, regular astigmatism, asymmetry (decentration or skewness), and higher-order irregular astigmatism. These 4 Fourier components were analyzed in both normal and pathologic eyes. Color-coded maps were generated to present the 4 Fourier components.

RESULTS

Color-coded mapping of the results of Fourier analysis of videokeratography data facilitated visual and instant interpretation of complex corneal topographic information. By using Fourier components, time course of changes in corneal topography following penetrating keratoplasty and influence of suture removal were quantitatively evaluated. The Fourier analysis method was successfully applied to determine the most appropriate correction lenses in eyes after penetrating keratoplasty.

CONCLUSIONS

Fourier analysis of videokeratography data allows mathematical separation of regular and irregular astigmatism and is useful in the quantitative assessment of corneal optics in eyes with both pathologic and postsurgical conditions.