title: Influence of corneal biomechanical properties on intraocular pressure differences between an air-puff tonometer and the Goldmann applanation tonometer.
abstract: OBJECTIVE
  To estimate the influence of corneal properties on intraocular pressure (IOP) differences between an air-puff tonometer (NT530P; Nidek) and the Goldmann applanation tonometer (Haag-Streit).
  
  
  METHODS
  The influence of central corneal thickness (CCT), keratometry, and Ocular Response Analyzer (Reichert) measurements of corneal viscoelasticity [corneal hysteresis (CH) and corneal resistance factor (CRF)] on IOP differences between tonometers was evaluated.
  
  
  RESULTS
  The CRF was calculated to be the best predictor of the differences in IOP readings between tonometers (r2=0.23; P<0.001), followed by CCT (r2=0.15; P=0.003) and CH (r2=0.14; P=0.003). Keratometry performed very poorly as lone predictor of IOP differences. In a multiple regression model, CRF, CH, and CCT together accounted for 25% (r2=0.25; P<0.01) of the variance in IOP reading differences between tonometers.
  
  
  CONCLUSIONS
  Corneal resistance to applanation induced by either contact or noncontact tonometers was calculated to be the most determinant factor in influencing IOP differences between applanation tonometers.
authors.affiliation: Dipartimento di Biopatologia e Diagnostica per Immagini, Sezione Oculistica, Università degli Studi Tor Vergata, Rome, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Tranchina
authors.forename: Marco
authors.initials: M
authors.lastname: Lombardo
authors.forename: Francesco
authors.initials: F
authors.lastname: Oddone
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Serrao
authors.forename: Domenico
authors.initials: D
authors.lastname: Schiano Lomoriello
authors.forename: Pietro
authors.initials: P
authors.lastname: Ducoli
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology*; D003315:Cornea / Q000502:physiology*; D063171:Corneal Pachymetry; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*; D055815:Young Adult