title: Comparison of the changes in corneal biomechanical properties after photorefractive keratectomy and laser in situ keratomileusis.
abstract: OBJECTIVE
  To compare the postoperative biomechanical properties of the cornea after photorefractive keratectomy (PRK) and after laser in situ keratomileusis (LASIK) in eyes with myopia.
  
  
  METHODS
  We retrospectively examined 27 eyes of 16 patients undergoing PRK and 31 eyes of 16 patients undergoing LASIK for the correction of myopia. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with Ocular Response Analyzer before and 3 months after surgery. We also investigated the relationship between these biomechanical changes and the amount of myopic correction.
  
  
  RESULTS
  The CH was decreased significantly from 10.8 +/- 1.3 (mean +/- SD) mmHg to 9.2 +/- 1.6 mmHg after PRK (P < 0.001), and from 10.8 +/- 1.4 mmHg to 8.6 +/- 0.9 mmHg after LASIK (P < 0.001). The CRF was also decreased significantly, from 10.3 +/- 1.5 mmHg to 8.4 +/- 1.8 mmHg after PRK (P < 0.001), and from 10.3 +/- 1.5 mmHg to 7.7 +/- 1.3 mmHg after LASIK (P < 0.001). The amount of decrease in CH and CRF was significantly larger after LASIK than after PRK (P = 0.04). There was a significant correlation between the amount of myopic correction and changes in biomechanical properties after PRK (r = -0.61, P < 0.01 for CH, r = -0.41, P < 0.05 for CRF) and LASIK (r = -0.37, P < 0.05 for CH, r = -0.45, P < 0.05 for CRF).
  
  
  CONCLUSIONS
  Both PRK and LASIK can affect the biomechanical strength of the cornea depending on the amount of myopic correction. The amount of biomechanical changes is larger after LASIK than after PRK. From a biomechanical viewpoint, PRK may be a less invasive surgical approach for the correction of myopia than LASIK.
authors: Department of Ophthalmology, University of Kitasato School of Medicine, Sagamihara, Kanagawa, 228-8555, Japan. kamiyak-tky@umin.ac.jp
authors: Kazutaka
authors: K
authors: Kamiya
authors: Kimiya
authors: K
authors: Shimizu
authors: Fumiko
authors: F
authors: Ohmoto
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology* / Q000601:surgery*; D018903:Photorefractive Keratectomy; D012189:Retrospective Studies; D055815:Young Adult