title: Intraocular pressure measurements and biomechanical properties of the cornea in eyes after penetrating keratoplasty.
abstract: OBJECTIVE
  To compare intraocular pressure (IOP) measurements obtained using the Goldmann applanation tonometer (GAT; Haag-Streit), the Tono-Pen XL (Reichert, Inc), and the ocular response analyzer (ORA; Reichert Ophthalmic Instruments), and to determine the influence of corneal factors on IOP measurements in eyes that had undergone penetrating keratoplasty (PK).
  
  
  METHODS
  Consecutive, prospective study.
  
  
  METHODS
  Study population. Sixty-one eyes that underwent PK were enrolled in this study. Intervention. IOP was measured using the GAT, Tono-Pen, and ORA. Corneal hysteresis and corneal resistance factor as provided by the ORA were recorded. Central corneal thickness was measured using an ultrasound pachymeter. Main outcome measures. IOP and corneal biomechanical factors.
  
  
  RESULTS
  IOP measurements were obtained in an average of 65 months (range, 6 to 209 months) after PK surgery. ORA-derived IOP measurements (corneal-compensated IOP and Goldmann-correlated IOP) and Tono-Pen XL IOP all correlated in a significant manner to GAT IOP measurements. Corneal-compensated IOP and Tono-Pen XL IOP values were higher than GAT IOP (P < .001 and P = .001, respectively), whereas Goldmann-correlated IOP readings did not differ from GAT IOP readings (P = .054). Central corneal thickness did not correlate to any tonometry technique. In a regression analysis, corneal hysteresis and corneal resistance factor were found to play a role in IOP prediction.
  
  
  CONCLUSIONS
  Central corneal thickness may be of less importance than corneal hysteresis and corneal resistance factor in IOP determination in eyes that have undergone PK, perhaps because of the lower modulus of elasticity in these eyes. GAT IOP seems to be lower than other tonometry techniques in eyes that have undergone PK.
authors.affiliation: Goldschleger Eye Institute, Sheba Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. didifabian@gmail.com
authors.forename: Ido D
authors.initials: ID
authors.lastname: Fabian
authors.forename: Irina S
authors.initials: IS
authors.lastname: Barequet
authors.forename: Alon
authors.initials: A
authors.lastname: Skaat
authors.forename: Ehud
authors.initials: E
authors.lastname: Rechtman
authors.forename: Mordechai
authors.initials: M
authors.lastname: Goldenfeld
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Roberts
authors.forename: Shlomo
authors.initials: S
authors.lastname: Melamed
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology*; D003315:Cornea / Q000503:physiopathology*; D003316:Corneal Diseases / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D015948:Keratoplasty, Penetrating; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014065:Tonometry, Ocular / Q000295:instrumentation; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult