Abstract:  Objective To compare the corneal ablation depth among three different types of laser surgery by online corneal pachymetry. Design Prospective comparative case series. Participants 200 eyes of 100 moderate and high myopia patients accepted laser surgery, including FEMTO-LASIK group 100 eyes of 50 patients, LASIK group 57 eyes of 30 patients and LASEK 43 eyes of 23 patients. Methods The corneal thickness was assessed intraoperatively with online optical coherence pachymetry (OCP) before and after laser ablation during surgery, and then the actual corneal ablation depth was calculated. The values of actual and theoretical ablation depth, and the difference in the three groups were compared. Main Outcome Measures Theoretical corneal ablation depth, actual corneal ablation depth. Results In FEMTO-LASIK group, the actual corneal ablation depth and theoretical ablation depth were117.22±31.13 μm and 99.52±25.47 μm respectively, t=-12.55, P<0.001; In LASIK group, the actual corneal ablation depth and theoretical ablation depth were 116.30±22.93 μm and 94.26±16.37 μm respectively, t=-12.44, P<0.001; In LASEK group, the actual corneal ablation depth and theoretical ablation depth were 106.72±23.77 μm and 99.31±20.46 μm respectively, t=-4.44, P<0.001. The difference between the actual corneal ablation depth and theoretical ablation depth were 17.69±14.10 μm in FEMTO-LASIK group, 22.04±13.38 μm in LASIK group and 7.41±10.95 μm in LASEK group. There were no difference between FEMTO-LASIK group and LASIK group, P=0.15, while the difference in LASIK and FEMTO-LASIK were significantly more than that of LASEK group, P<0.001. Conclusions The actual corneal ablation depth is more than theoretical ablation measured by online OCP during three different types of laser surgery. The difference between the actual corneal ablation depth and theoretical ablation depth should be taken into consideration while calculating the corneal stroma thickness preoperatively. (Ophthalmol CHN, 2014, 23: 305-307)

Key words: cornea refractive surgery, corneal thickness, ablation depth