Quantifying Corneal Toricity From Videokeratography With Fourier Analysis

BACKGROUND: Fourier analysis can be used to quantify corneal toricity from videokeratography data. This study measures the repeatability of Fourier-derived toricity values in normal adult corneas. METHODS: The Topographic Modeling System (TMS) was used to model the corneas of 29 subjects on two occasions, and Fourier analysis applied to the data. Repeatability of Fourier-derived toricity values between sessions was examined, and 95% limits of agreement were established. RESULTS: The 95% limits of agreement between sessions for the Fourier method were -0.02 +/- 0.16 diopters (D) and -0.5 +/- 5.7 degrees for toricity amount and axis, respectively. CONCLUSIONS: The Fourier method yields highly repeatable toricity values and thus provides a sensitive means of detecting longitudinal toricity change in normal corneas.