Comparison of the Changes in Corneal Biomechanical Properties after Photorefractive Keratectomy and Laser in Situ Keratomileusis Using Ocular Response Analyzer

Abstract
Background: Correction of vision using Photorefractive Keratectomy (PRK) or Laser In Situ Keratomileusis (LASIK) flap creation associated with ablation produces profound changes in the corneal structure and biomechanical properties secondary to central thinning and disruption of collagen lamellar continuity.
Aim of Work: This study aims to compare the changes in corneal biomechanical properties after PRK and LASIK in the treatment of low and moderate myopia by Ocular Response Analyzer.
Subjects and Methods: This study included 42 adult eyes divided into two groups: (1) Contain 21 eyes referred for Lasik surgery. (2) Contain 21 eyes referred for PRK surgery. Ocular Response Analyzer (ORA) was applied to each group to measure Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF).
Results: There was no statistically significant difference in CH and CRF, and between CCT and RSB between the two studied groups. There was statistically significant decrease in CH after both LASIK and PRK. There was statistically significant decrease in CRF after both LASIK and PRK. There was statistically significant difference in SE after LASIK and PRK. There was statistically significant difference between LASIK and PRK in CH and CRF change with more decrease after LASIK.
Conclusion: PRK and LASIK substantially weaken the biomechanical strength of the cornea, depending on the amount of archived myopic correction, and that the changes in corneal biomechanics were larger after LASIK than after PRK.