Following the simulations, anterior corneal surface coordinates of pre- and posttreatment geometries were exported from Abaqus Version 6.11 (Dassault Systemes Simulia Corp.). Using the pre- and posttreatment anterior surface coordinates from both simulated and clinical geometries, simulated
K values including mean tangential curvature from the central 3-mm region (
Kmean), the average curvature of the steepest meridian (
K1), and the average curvature of the flattest meridian (
K2) of the anterior corneal surface were calculated. Tangential curvature at each point (
Ktan) on the cornea was calculated using the first and second derivative of an 8
th order Zernike fit (Z) of the anterior corneal surface with respect to distance from the center of the cornea (
rcornea) (
Equation 9). The constants of Zernike polynomials (Z) were calculated with a linear regression analysis using a custom Python script. The calculated tangential curvature values were converted to diopters (D) using Snell‘s law with a corneal refractive index of 1.3375 (the keratometric index, which estimates the total corneal power assessed at the anterior corneal surface). Pretreatment clinical K
1 and K
2 values were directly taken from Pentacam tomographies for comparison. Pretreatment model, posttreatment clinical, and simulated K
1 and K
2 values were calculated using SpecifEye. The pairwise differences of these variables for clinical and simulated geometries were calculated. Statistical significance was determined by paired Student's
t-tests for nonindependent samples with
P less than 0.05 indicating significance (MINITAB, Minitab, Inc., State College, PA, USA).