High-order aberration changes after femtosecond LASIK surgery in patients with high myopia.

BACKGROUND: To investigate the relationship between high-order aberration (HOA) changes and RCST/CT (residual corneal stroma thickness/corneal thickness) after femtosecond LASIK surgery. METHODS: A total of 65 eyes from 39 patients with high myopia, who had femtosecond (FS) laser-assisted in situ keratomileusis (LASIK) surgery performed in our hospital, were included in this study. HOA and central corneal thickness were measured preoperatively and at 1 week, 1 month, and 3 months after FS-LASIK by Sirius Scheimpflug-Placido topography. Residual corneal stroma thickness (RCST) and ablation depth were measured during surgery. RESULTS: Horizontal coma (Z31), spherical aberration (Z40), second horizontal coma (Z51), second horizontal trefoil (Z53), pentafoil (Z55), second spherical aberration (Z60), and total HOAs were significantly increased at 1 week, 1 month, and 3 months after surgery compared with the preoperative values (P<0.05), but no significant differences were found in horizontal trefoil (Z33; P>0.05). Furthermore, Z31, Z40, and HOAs were significantly increased at 3 months post-surgery compared with the values at 1 week post-operation (P<0.05). Positive correlations were found between ablation depth and Z60 at 1 week and 1 month after surgery (r=0.291 and 0.337, respectively; P<0.05). Ablation depth was positively correlated with Z40 and Z60 at 3 months after surgery (r=0.439 and 0.336, respectively; P<0.05). The RCST/CT was negatively correlated with Z40, Z60, and HOAs at 3 months after surgery (r=-0.322, -0.412, and -0.321, respectively; P<0.05). There were no significant correlations between Zernike coefficients in terms of high-order aberration, HOAs, and RCST/CT at 1 week and 1 month post-surgery. CONCLUSIONS: Corneal HOAs in high myopia patients increased significantly after FS-LASIK surgery, and this was mainly observed as increases in coma and spherical aberration. The greater the ablation depth, the larger the influence on spherical aberrations. The greater the RCST/CT, the smaller the influence of HOAs on the cornea.

Effect of related factors on the stability of posterior corneal surface after LASIK / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To discuss the related factors that affected the stability of posterior corneal surface after laser in situ keratomileusis ( LASIK) . METHODS:About 64 patients (64 eyes) were enrolled. The correlation among the changes in posterior corneal surface 6 month after LASIK, surgery method, corneal flap thickness ( FT ) , ablation thickness ( AT ) , postoperative residual corneal stroma thickness ( RCST ) , preoperative thinnest corneal thickness ( CT ) , flap thickness/preoperative thinnest corneal thickness ( FT/CT ) , ablation thickness/preoperative thinnest corneal thickness ( AT/CT) , postoperative residual corneal stroma thickness/preoperative thinnest corneal thickness ( RCST/CT) , anterior and posterior preoperative corneal height, the difference of the forward shift in posterior corneal surface ( diff value ) of preoperative and preoperative intraocular pressure were analyzed. RESULTS: The changes of diff value between preoperative and postoperative were related with diopter (r=0.419, P=0.014), AT (r=0.394, P=0.023), AT/CT (r=0.501, P=0.004), Diff value of preoperative (r=0.501, P=0. 004), RCST (r=-0. 385, P=0. 033) and RCST/CT (r=-0. 401, P=0. 025). The changes of height value from posterior corneal surface between preoperative and postoperative were related with diopter (r=0. 520, P=0. 002), AT (r=0.504, P=0. 003), AT/CT (r=0. 442, P=0. 013), Diff value of preoperative (r=0. 624, P=0. 000) and RCST/CT (r=-0. 394, P=0. 028). CONCLUSION: AT, RCST, AT/CT, RCST/CT and diff value of preoperative should be the key index that predicted the stability of posterior corneal surface after LASIK,the further research will give the range of safety value.