title: Validation of the Barraquer tonometer for high intraocular pressure estimation.
abstract: OBJECTIVE
  To compare the pneumatonometer and the Tono-Pen XL in a closed ex-vivo system in human eye bank eyes at high intraocular pressures (IOP) and evaluate the validity of high IOP measurements with the Barraquer tonometer.
  
  
  METHODS
  Intraocular pressure was monitored by cannulation of the anterior chamber and vitreous cavity in eight human cadaver eyes (mean donor age: 77.3 +/- 4.9 years, range: 72 to 84 years). Intraocular pressure measurements were taken at 50, 65, and 90 mmHg with the Tono-Pen XL and pneumatonometer. Intraocular pressure was raised to 110 mmHg and then the eyes were deflated slowly until they reached 50 mmHg. Pressure readings with the Barraquer tonometer were recorded when the corneal tonometer interface reached the inner and outer rings.
  
  
  RESULTS
  The Tono-Pen XL underestimated IOP, a tendency that was more evident at higher IOP In contrast, the pneumatonometer was more accurate and reliable at IOP of 50 and 65 mmHg but its readings underestimated IOP at 90 mmHg. The Barraquer tonometer used in this experiment accurately estimated high IOP A variability of 5.9 mmHg and 5.8 mmHg were recorded for the inner and outer ring, respectively.
  
  
  CONCLUSIONS
  The Tono-pen XL is an inadequate instrument to assess pressures normally encountered during LASIK flap creation in an ex vivo model using human cadaver eyes. The pneumatonometer and the Barraquer tonometer are accurate instruments at high IOP; however, the pneumatonometer underestimated pressures around 90 mmHg.
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 1638 NW 10 Ave, Miami, FL 33136, USA.
authors.forename: Edgar M
authors.initials: EM
authors.lastname: Espana
authors.forename: Ana C
authors.initials: AC
authors.lastname: Acosta
authors.forename: Izuru
authors.initials: I
authors.lastname: Nose
authors.forename: Marcia
authors.initials: M
authors.lastname: Orozco
authors.forename: Francisco
authors.initials: F
authors.lastname: Fantes
authors.forename: Sonia H
authors.initials: SH
authors.lastname: Yoo
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Parel
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000867:Anterior Chamber / Q000502:physiology; D002102:Cadaver; D004867:Equipment Design; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*