Group differences for continuous variables were tested using the paired Student t tests. The change in manifest refraction (spherical equivalent) (MRSE) and topographic k values and topographic astigmatism were plotted over time to determine long-term stability, and the difference as a function of time was analyzed using paired 2-tailed t tests (at time intervals of preoperative to 1 month, 1 to 3 months, 3 to 6 months, 6 to 12 months, and every year of follow up period). Results are presented as means + standard deviation [SD]. A P value less than .05 was regarded as statistically significant.