Evaluating surgically induced astigmatism by Fourier analysis of corneal topography data

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Abstract
Incision based on the axis of the steepest meridian. We performed conventional keratometry and corneal topography before and up to 1 month after surgery. Using Fourier analysis, the corneal topographic images were broken into spherical power, regular astigmatism, and nonregular astigmatism for individual or aggregate analysis of surgically induced astigmatism. The induced refractive change (average of the difference between preoperative and postoperative corneal topographies) was analyzed and normalized according to the surgical meridian and to right/left eye. Results: Regular astigmatism calculated by Fourier analysis of mires from the keratometer zone correlated well with conventional keratometry readings. Surgery induced a localized flattening in the superior region and a with-the-rule regular astigmatism component in the central area. Conclusion: Surgically induced corneal topography changes can be analyzed by Fourier series harmonic analysis, allowing aggregate data to be broken into optically meaningful quantities. aReprint requests to Thomas Olsen, MD, Department of Ophthalmology, Aarhus University, Aarhus Kommunehospital, DK-8000 Aarhus C, Denmark. Presented at the 13th Congress of the European Society of Cataract and Refractive Surgeons, Amsterdam, October 1995. Supported by Landsforeningen til Bekampehe of Øjensygdomme og Blindbed and Karen Elise Jensens Fond. © Williams & Wilkins 1996. All Rights Reserved....

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