title: Intra- and postoperative variation in ocular response analyzer parameters in keratoconic eyes after corneal cross-linking.
abstract: OBJECTIVE
  To analyze intra- and postoperative variation in Ocular Response Analyzer (ORA, Reichert Ophthalmic Instruments) parameters in 24 keratoconic eyes undergoing corneal cross-linking (CXL).
  
  
  METHODS
  In a prospective clinical study, corneal hysteresis (CH), corneal resistance factor (CRF), peak 1 and peak 2 amplitude, corneal-compensated and Goldmann-correlated intraocular pressure (IOP) were evaluated using the ORA. The thinnest cornea point was measured with the Pentacam (Oculus Inc). Corneal topography and endothelial cell count were performed. Measurements were recorded at baseline; intraoperatively after epithelium removal, riboflavin impregnation, and ultraviolet A irradiation; and postoperatively after corneal re-epithelialization and at 1, 6, and 12 months.
  
  
  RESULTS
  A statistically significant reduction of the thinnest cornea point from 462±23.24 μm was observed at the end of the CXL procedure intraoperatively and at 1- and 6-month follow-up (P<.05). A significant increase in the thinnest cornea point to 624±31.72 μm was found after re-epithelialization (P<.05), and no significant changes were observed at 1 year postoperatively. Mean CH and CRF did not change significantly after de-epithelialization, but were noted to significantly increase after CXL intraoperatively and postoperatively at 1-month follow-up. At 6 and 12 months postoperatively, CH and CRF were not statistically significantly different from pre-operatively. Peak 1 and peak 2 decreased intraoperatively from 276±52 and 228±47 to 172±42 and 131±42, respectively, at the conclusion of CXL (P<.05), and were noted to increase to 493±41 and 444±51, respectively, at 6-month follow-up. Corneal-compensated IOP and Goldmann-correlated IOP increased at 1 month after CXL (P>.05).
  
  
  CONCLUSIONS
  The results showed a significant change in ORA parameters and the thinnest cornea point during and after the CXL procedure and a high correlation between peak amplitudes and corneal asymmetry, providing insight to the bioelastic and biomechanical behavior of the cornea during and after CXL.
authors.affiliation: Department Ophthalmology, Istituto Clinico Humanitas, Rozzano, Milan, Italy. info@vincieye.it
authors.forename: Paolo
authors.initials: P
authors.lastname: Vinciguerra
authors.forename: Elena
authors.initials: E
authors.lastname: Albè
authors.forename: Ashraf M
authors.initials: AM
authors.lastname: Mahmoud
authors.forename: Silvia
authors.initials: S
authors.lastname: Trazza
authors.forename: Farhad
authors.initials: F
authors.lastname: Hafezi
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Roberts
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology*; D003094:Collagen / Q000378:metabolism; D003315:Cornea / Q000503:physiopathology*; D003319:Corneal Stroma / Q000378:metabolism; D019781:Corneal Topography; D003432:Cross-Linking Reagents; D005260:Female; D006801:Humans; D007429:Intraocular Pressure; D007432:Intraoperative Period; D007640:Keratoconus / Q000188:drug therapy* / Q000503:physiopathology*; D008297:Male; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011184:Postoperative Period; D011446:Prospective Studies; D012256:Riboflavin / Q000627:therapeutic use; D014466:Ultraviolet Rays; D055815:Young Adult
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin