Biomechanical corneal effects of LASIK Xtra compared with conventional FS-LASIK in high myopic eyes

Purpose:To investigate the in vivo corneal biomechanical response to FS-LASIK combined with accelerated corneal crosslinking (LASIK Xtra) compared with conventional FS-LASIK (convLASIK) in highly myopic eyes. Setting:Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany. Design:Prospective, randomized fellow eye-controlled clinical trial. Methods:Patients who received treatment with LASIK Xtra (30mW/cm(2), 90 seconds with continuous UV-A) in 1 eye and convLASIK in the other eye were enrolled. Both eyes were subjected preoperatively and 12 months postoperatively to a Corvis ST examination. The stiffness parameter at first applanation (SP-A1), integrated inverse radius (IIR), deformation amplitude (DA), deformation amplitude 2 mm away from apex, and the apical deformation (DARatio2mm) were evaluated. Results:The study included 38 high myopic eyes (-7.34 +/- 1.02 diopters) of 19 patients. The results of the corneal biomechanical measurement showed a significant reduction in overall corneal stiffness with a significant decrease in postoperative SP-A1 and increase in IIR, DA, and DARatio2mm (P < .001). In a direct comparison, there was no evidence of an increase in corneal stiffness in the LASIK Xtra group compared with the convLASIK group 12 months postoperatively. No statistically significant difference was detected in any of the 4 biomechanical parameters (P > .05). Conclusions:The corneal biomechanical response to convLASIK and LASIK Xtra did not vary significantly. With a similar corneal thickness loss, there was no significant difference in the 4 biomechanical metrics between the convLASIK and LASIK Xtra groups. Thus, LASIK Xtra appeared not to have a protective corneal stiffening effect compared with convLASIK 12 months postoperatively.