Evaluation of Corneal Biomechanics After Excimer Laser Corneal Refractive Surgery in High Myopic Patients Using Dynamic Scheimpflug Technology

Objective: To compare the effect of femtosecond-assisted thin flap laserassisted in situ keratomileusis (FS-LASIK) and photorefractive keratectomy with mitomycin-C (PRK-MMC) in highly myopic patients (. 7.0 D [ D]) on corneal biomechanical parameters. Methods: In this prospective comparative interventional case series, 60 patients (30 patients in each group) with a manifest refractive spherical equivalent (MRSE) greater than 7.0 D were enrolled. Corvis ST parameters were measured before and at 3 and 6 months postoperatively. Results: Preoperatively, mean MRSE was 28.6561.51 D in FS-LASIK and 28.0461.70 D in PRK-MMC groups (P = 0.149), and corneal thickness was 570.67636.79 mm and 507.12632.55 mm, respectively (P < 0.001). At 6 months, both groups showed significantly higher applanation (A) 2 time and A2-velocity (P < 0.05 in both), whereas intraocular pressure (IOP), corrected IOP, A1 time, A1-velocity, and radius at highest concavity were significantly reduced (P, 0.05 in all). In the FS-LASIK group, there was a significant increase in deformation amplitude (DA) (P = 0.001), and significant decreases in A2-length (P = 0.004). Peak distance increased in the PRK-MMC group (P = 0.029). At 6 months, after controlling for fellow eye correlations and preoperative corneal thickness between the two groups, decreases in IOP, A1-time, A2-length and radius, and the increase in DA was greater in FS-LASIK. Conclusion: This study demonstrated significant changes in Corvis ST ocular biomechanical metrics after both PRK-MMC and FS-LASIK in high myopic patients, indicating the significant effect of excimer laser refractive surgery on corneal biomechanical properties. However, changes that occur with FS-LASIK are more significant than with PRK-MMC. Further randomized studies are needed to better characterize the pattern of biomechanical changes associated with each type of surgery.