Figure 5 Decomposition of corneal topography (by Fourier analysis) into the four main aberration components (spherical‐like, coma‐like, regular astigmatism and irregular astigmatism) for a spherical (A), an elliptical (B) and a mixed ablation (C). Note the similarity between the regular astigmatic component and the pure secondary regular astigmatism (horizontal) representations in the Zernike pyramid on the right side for the elliptical ablation (sixth order horizontal astigmatism, B) and mixed ablation (fourth order horizontal astigmatism, C).