[A clinical study of actual corneal ablation depth in laser in situ keratomileusis].

PURPOSE:To assess the predictability of corneal ablation depth in LASIK using NIDEK EC5000 excimer laser. METHODS:Standard LASIK surgery was performed in 79 myopic patients with or without astigmatism with the NIDEK EC5000 excimer laser system.Ultrasonic corneal pachymetry was performed immediately after flap creation and after laser ablation during LASIK procedure,by which the actual corneal ablation depth was calculated.The values of actual and predicted ablation depth were compared. RESULTS:The actual ablation depth was (92.32+/-29.86)μm, the predicted ablation depth was (74.16+/-25.95)μm.The differences between them(18.16+/-14.71)μm were statistically significant(p<0.001).Linear regression suggested that the actual ablation depth correlated closely with the predicted ablation depth(r=0.87,p<0.001).The regression model was Y=18.06+1.001X.The differences remained statistically significant and were independent of the levels of preoperative corneal keratometry,absolute preoperative spherical equivalent and the preoperative central cornea thickness. CONCLUSIONS:The actual ablation depth was about(18.16+/-14.71)μm thicker than the predicted ablation depth in the NIDEK EC5000 excimer laser system. We may have to take into account this deviation in order to ensure sufficient thickness of residual stromal bed.