Purpose To describe the effect of the corneal asphericity and toricity on the map patterns and Best Fit Sphere (BFS) characteristics in elevation topography. Methods The corneal surface was modeled as a biconic surface of principal radii and asphericity values of (r1, r2) and (Q1, Q2), respectively. The apex of the biconic surface corresponded to the origin of a polar coordinates system. Minimization of the squared residuals was used to calculate the values of the radii of the best fit spheres (BFS) and apex distance (A-values :z distance between the corneal apex and the BFS) of the modelled corneal surface for various configurations relating to commonly clinical measured values of apical radius, asphericity and toricity. Results Increased apical radius of curvature and increased prolateness (negative asphericity) led to an increase in BFS radius, but had opposite effects on the A-value. Increased prolateness resulted in increased BFS radius and A-value. Increasing toricity did not alter these findings. Color-plot elevation maps of the modelled corneal surface showed complete ridge patterns when toricity was increased and showed incomplete ridge and island patterns when prolateness was increased. Conclusions High A-values in patients with corneal astigmatism may result from steep apical curvature and/or high prolateness (negative asphericity). The BFS radius may help in distinguishing between these two causes of increased A-values. Increased prolateness and decreased apical radius of curvature (often seen in keratoconus) have opposite effects on the BFS radius but similar effects on the apex distance.