Factors affecting the forward shift of posterior corneal surface after laser in situ keratomileusis

Purpose: To evaluate the anteroposterior movement of the corneal back surfa ce after laser in situ keratomileusis (LASIK), Design: Retrospective noncomparative case series, Participants: One hundred ninety-six eyes of 120 subjects with myopic refra ctive errors of -2.0 to -12.5 diopters, Intervention: LASIK was performed. Corneal topography of the posterior corn eal surface was obtained with the scanning slit topography system before an d 1 month after surgery. Main Outcome Measures: The amount of forward shift of the posterior corneal surface was determined. Multiple regression analysis was used to assess th e factors that affect the forward shift of the posterior corneal surface. Results: After surgery, the posterior corneal surface displayed mean forwar d shift of 40.9 +/- 24.8 mum. Explanatory variables relevant to the forward shift of corneal posterior surface were, in the order of magnitude of infl uence, the amount of laser ablation (partial regression coefficient B = 0.5 61, P < 0.0001), preoperative corneal thickness (B = -0.176, P = 0.00096), and preoperative intraocular pressure (B = 1.676, P = 0.0053), Preoperative refraction and achieved myopic correction showed collinearity with the amo unt of laser ablation, Conclusions: LASIK induces a forward shift of the cornea, Eyes with thinner corneas, higher intraocular pressure, and higher myopia requiring greater laser ablation are more predisposed to the anterior shift of the cornea, Op hthalmology 2001;108:317-320 (C) 2001 by the American Academy of Ophthalmol ogy.