title: Determination of corneal elasticity coefficient using the ORA database.
abstract: OBJECTIVE
  To propose a new approach for the study of corneal biomechanics using the Reichert Ocular Response Analyzer (ORA) database, which is based on changes in velocity retardation in the central cornea at the peak of flattening.
  
  
  METHODS
  The ORA applanation curve was analyzed using a mathematical technique, which allowed calculation of the elasticity coefficient (Ke), which is primarily characteristic of the elastic properties of the cornea. Elasticity coefficient values were obtained in patients with presumably different biomechanical properties of the cornea: "normal" cornea (71 eyes, normal group), keratoconus (34 eyes, keratoconus group), LASIK (36 eyes, LASIK group), and glaucoma with elevated and compensated intraocular pressure (lOP) (38 eyes, glaucoma group).
  
  
  RESULTS
  The mean Ke value in the normal group was 11.05 +/- 1.6, and the corneal thickness correlation coefficient r2 was 0.48. In the keratoconus group, the mean Ke value was 4.91 +/- 1.87 and the corneal thickness correlation coefficient r2 was 0.47. In the LASIK group, Ke and r2 were 5.99 +/- 1.18 and 0.39, respectively. In the glaucoma group, the same eyes that experienced a two-fold reduction in lOP developed a statistically significant reduction in the Ke (1.06 times lower), whereas their corneal hysteresis value increased 1.25 times.
  
  
  CONCLUSIONS
  The elasticity coefficient calculated using the ORA applanation curve can be used in the evaluation of corneal biomechanical properties.
authors.affiliation: Research Institute of Eye Diseases of the Russian Academy of Medical Sciences, Moscow, Russia.
authors.forename: Sergei E
authors.initials: SE
authors.lastname: Avetisov
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Novikov
authors.forename: Irina A
authors.initials: IA
authors.lastname: Bubnova
authors.forename: Alexei A
authors.initials: AA
authors.lastname: Antonov
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Siplivyi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D003315:Cornea / Q000503:physiopathology*; D004548:Elasticity / Q000502:physiology*; D006801:Humans; D007429:Intraocular Pressure; D007640:Keratoconus / Q000503:physiopathology*; D020731:Keratomileusis, Laser In Situ; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology* / Q000601:surgery; D009798:Ocular Hypertension / Q000503:physiopathology*; D055815:Young Adult