RESUMO
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.
RESUMO
PURPOSE: We compared laser assisted in situ keratomileusis (LASIK) mode and photorefractive keratectomy (PRK) mode ablation methods in laser subepithelial keratomileusis (LASEK) surgery using the MEL-80 excimer laser. METHODS: All patients were followed up for a minimum of 1 year. The PRK mode group consisted of 46 eyes of 23 patients and the LASIK mode group consisted of 97 eyes of 56 patients. The central corneal thickness (CCT), ablation thickness, manifest refractive error and uncorrected visual acuity were compared preoperatively, 1 month and 1 year postoperatively. Spherical equivalent (SE) of cycloplegic refraction at postoperative 1 month and the uncorrected visual acuity (UCVA) ratios of 1.0 or better at postoperative 1 year were compared between the two groups to evaluate clinical efficacy. RESULTS: The SE of refractive error, CCT and target corneal ablation thickness of the two groups were not significantly different preoperatively. The PRK mode group obtained an actual ablation mean thickness of 82.8% of the target and the LASIK mode group obtained an actual ablation mean thickness of 94.1% of the target at postoperative 1 month. In each group, a statistically significant difference was observed between the actual corneal ablation thickness and target corneal ablation thickness. In the PRK mode group, the mean SE of postoperative 1 month cycloplegic refraction was +0.24 +/- 0.47 D and in the LASIK mode group, +0.87 +/- 0.54 D, indicating a statistically significant difference between the two groups. One year postoperatively, the UCVA ratios of 1.0 or better were 83% in the PRK mode group and 96% in the LASIK mode group, showing a statistically significant difference between the two groups. However, SE of manifest refractive error and CCT in the two groups were not statistically different at postoperative 1 year. CONCLUSIONS: The LASIK mode ablation method showed better results than the PRK mode ablation method in postoperative UCVA prognosis after LASEK surgery using the MEL-80 excimer laser.
