title: Biomechanical parameters of the cornea after collagen crosslinking measured by waveform analysis.
abstract: OBJECTIVE
  To compare 2 corneal biomechanical parameters--corneal hysteresis (CH) and corneal resistance factor (CRF)--before and after collagen crosslinking (CXL) for keratoconus.
  
  
  METHODS
  Eye Research Center of Mashhad University of Medical Sciences, Khatam-al-Anbia Eye Hospital, Mashhad, and Department of Ophthalmology, Baqiyatallah University of Medical Science, Tehran, Iran.
  
  
  METHODS
  Case series study.
  
  
  METHODS
  Topical riboflavin was applied to the deepithelialized cornea every 3 minutes for 30 minutes and every 5 minutes during ultraviolet-A irradiation of the cornea. Corneal hysteresis and CRF were measured by biomechanical waveform analysis (Ocular Response Analyzer) before and 6 months after CXL. The values were compared using the paired Student t test.
  
  
  RESULTS
  The study comprised 51 patients (56 eyes). The mean age of the patients was 23.27 years ± 6.3 (SD). Before CXL, the mean CH was 7.9 ± 1.5 mm Hg and the mean CRF was 7.3 ± 1.4 mm Hg. Six months after CXL, the mean values were 8.20 ± 1.5 mm Hg and 7.59 ± 1.5 mm Hg, respectively. The changes in CH and CRF were not statistically significant (P>.05). The changes in central corneal thickness and Goldmann-correlated intraocular pressure (IOP) between preoperatively and postoperatively were not statistically significant, although the change in corneal-compensated IOP was (P<.05).
  
  
  CONCLUSIONS
  Although previous in vitro studies found a change in corneal rigidity, this study found no significant change in CH or CHF measured by biomechanical waveform analysis.
authors.affiliation: Khatam-Al-Anbia Eye Hospital, Mashad University of Medical Science, Mashad, Iran.
authors.forename: Mohamadreza
authors.initials: M
authors.lastname: Sedaghat
authors.forename: Mostafa
authors.initials: M
authors.lastname: Naderi
authors.forename: Mehran
authors.initials: M
authors.lastname: Zarei-Ghanavati
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism / Q000503:physiopathology*; D003432:Cross-Linking Reagents; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D007640:Keratoconus / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012029:Refraction, Ocular / Q000502:physiology; D012256:Riboflavin / Q000627:therapeutic use*; D014466:Ultraviolet Rays; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin