Biomechanical Corneal Effects of LASIK-Xtra Compared to Conventional Femto-LASIK in High Myopic Eyes.

Abstract

Purpose: This study seeks to investigate the in vivo corneal biomechanical response to femtosecond laser-assisted in situ keratomileusis (FS-LASIK) combined with accelerated corneal crosslinking (LASIK-Xtra) compared to conventional FS-LASIK (convLASIK) in highly myopic eyes.

Setting: Department of Ophthalmology, Goethe-University, Frankfurt, Germany.

Design: A prospective, randomized fellow eye-controlled clinical trial.

Methods: We enrolled patients who received treatment with LASIK-Xtra (30mW/cm 2 , 90 seconds with continuous UVA) in one eye and convLASIK in the fellow eye. Both eyes were subjected preoperatively and twelve 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 diopter) 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 to the convLASIK group twelve months postoperatively. No statistically significant difference was detected in any of the four biomechanical parameters (p>.05).

Conclusion: 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 four biomechanical metrics between the convLASIK and LASIK-Xtra groups. Thus, LASIK-Xtra seems not to have a protective corneal stiffening effect compared to convLASIK twelve months postoperatively.