Aims-To quantitatively evaluate the changes in corneal irregular astigmatis
m after laser in situ keratomileusis (LASIK) in relation to the amount of l
aser ablation.
Methods-In 189 eyes of 116 patients undergoing LASIK for myopia, corneal to
pography was obtained before and 1 month after surgery. Using Fourier harmo
nic analysis of the topography data, corneal irregular astigmatism (asymmet
ry and higher order irregularity) was calculated.
Results-By surgery, asymmetry component significantly increased (p < 0.0001
, Wilcoxon signed rank test), while higher order irregularity did not (p =
0.767). The increases in the asymmetry component significantly correlated w
ith ablation depth (Spearman rank correlation coefficient r(s) = 0.440, p <
0.0001). No significant correlation was found between changes in higher or
der irregularity and ablation depth (r(s) = 0.137, p = 0.074).
Conclusion-LASIK significantly increases the asymmetry component of the cor
nea which is dependent on the amount of laser ablation.