Comparision Of Forward Shifts Of Posterior Corneal Surface And Changes Of Anterior Chamber Depth After Lasik And Lasek

Objective: To compare and evaluate the changes in forward shifts of posterior corneal surface and anterior chamber depth after laser in situ keratomileusis (LASIK) and laser subepithelial keratomileusis (LASEK).Methods: Thirty four eyes from eighteen patients who underwent LASIK and twenty two eyes from twelve patients who underwent LASEK were included in this study. Before surgery, the refractive errors, posterior best-fit sphere power, corneal thickness and ablation depth were no difference in both groups. Posterior best-fit sphere power, diff value, different—diff value and anterior chamber depth were obtained and compared with the OrbscanⅡcorneal topography analysis before and 3 month after surgery.Results: In the LASIK group, the postoperative RBT was 300.12μm (290.00μm～315.0μm) . In the LASEK group, the postoperative RBT was 465.45μm (453.00μm～477.00μm). For LASIK, before surgery, the posterior corneal surface displayed posterior best-fit sphere power of 52.04D (49.30D～53.90D) , diff value of 25.29μm ( 10.00μm～37.00μm ) , anterior chamber depth of 3.29mm(3.00mm～3.59mm). For LASEK, before surgery, the posterior corneal surface displayed posterior best-fit spheres power of 53.06D (49.10D～56.20D) , diff value of 29.91μm ( 19.00μm～40.00μm ) , anterior chamber depth of 3.14mm(2.90mm～3.61mm). For LASIK, 3 month after surgery, the posterior corneal surface displayed the mean posterior best-fit sphere power of 52.21D (49.80D～ 54.40D) , diff value of 32.56μm (21.00μm～55.00μm) , different-diff value of 21.88μm (14.00μm～36.00μm) , anterior chamber depth of 3.23mm(2.90mm～3.47mm). For LASEK, 3 month after surgery, the posterior corneal surface displayed the mean posterior best-fit sphere power of 52.70D (50.10D～54.90D) , diff value of 35.63μm (26.00μm～45.00μm) , different-diff value of 22.18μm (12.00μm～41.00μm) , anterior chamber depth of 3.14mm(2.86mm～3.49mm). For LASIK, the posterior best-fit sphere power and the anterior chamber depth (ACD) before the surgery and 3 months after the surgery were no significant difference(P>0.05). There was significant difference in the diff value for LASIK (P <0.05) . And LASEK was the same. For the posterior best-fit sphere power, diff value and different-diff value, there was no significant difference 3 month after surgery between LASIK and LASEK (P>0.05) .Conclusions: LASIK and LASEK induce the forward shift of posterior corneal surface. There was no significant difference between LASIK and LASEK 3 month after surgery in the posterior best-fit sphere power, diff value and different-diff value (P >0.05) . In both groups, there was no difference in the anterior chamber depth (ACD) before and 3 months after the surgery. If we will operate on the medium myopia patients for LASIK, LASIK and LASEK are all suitable as long as the expectant corneal residual bed thickness >290μm.