title: Comparison of Diaton transpalpebral tonometer with applanation tonometry in keratoconus.
abstract: OBJECTIVE
  To investigate the added value of using a Diaton transpalpebral tonometer (DT) to measure IOP in keratoconus. Most type of tonometers use corneal applanation or biomechanical resistance to measure intraocular pressure (IOP); however, these factors can be altered by keratoconus. Specifically, we examined whether DT can detect false-negative low Goldmann applanation tonometry (AT) measurements.
  
  
  METHODS
  Patients with keratoconus were recruited from our tertiary academic treatment center. Measurements included AT and DT (in random order) and Scheimpflug imaging. An age- and gender-matched group of control subjects with no history of corneal disease or glaucoma was also recruited.
  
  
  RESULTS
  In total, 130 eyes from 66 participants were assessed. In the keratoconus group, mean AT was 11.0 ± 2.6, mean DT 11.2±5.5 (P=0.729), and the two measures were correlated significantly (P=0.006, R=0.323). However, a Bland-Altman plot revealed a wide distribution and poor agreement between both measurements. Previous corneal crosslinking, corneal pachymetry, and Krumeich classification had no effect on measured IOP.
  
  
  CONCLUSIONS
  Measurements obtained using a Diaton tonometer are not affected by corneal biomechanics; however, its poor agreement with Goldmann AT values calls into question the added value of using a Diaton tonometer to measure IOP in keratoconus.
authors.affiliation: Utrecht Corneal Research Group Department of Ophthalmology, University Medical Center Utrecht, Utrecht 3508 GA, The Netherlands.
authors.forename: Robert Pl
authors.initials: RP
authors.lastname: Wisse
authors.affiliation: Utrecht Corneal Research Group Department of Ophthalmology, University Medical Center Utrecht, Utrecht 3508 GA, The Netherlands.
authors.forename: Natalie
authors.initials: N
authors.lastname: Peeters
authors.affiliation: Utrecht Corneal Research Group Department of Ophthalmology, University Medical Center Utrecht, Utrecht 3508 GA, The Netherlands.
authors.forename: Saskia M
authors.initials: SM
authors.lastname: Imhof
authors.affiliation: Utrecht Corneal Research Group Department of Ophthalmology, University Medical Center Utrecht, Utrecht 3508 GA, The Netherlands.
authors.forename: Allegonda
authors.initials: A
authors.lastname: van der Lelij
keywords: Bland-Altman plot; Diaton; Goldmann applanation tonometry; keratoconus; transpalpebral tonometry