title: Hand-held dynamic contour tonometry.
abstract: OBJECTIVE
  We present a prototype of the hand-held dynamic contour tonometer (HH-DCT) and prospectively compare this HH-DCT with the well-established Perkins applanation tonometer (PAT) and the TonoPenXL (TPXL).
  
  
  METHODS
  In a prospective, single-centre, randomized study, intraocular pressure (IOP) readings were taken in random order using HH-DCT, PAT and TPXL tonometers. Intra-observer variability was calculated for each observer and compared between three experienced ophthalmologists and an inexperienced medical student.
  
  
  RESULTS
  Ninety-two corneas of 92 healthy participants were enrolled. IOP [mean mmHg ± standard deviation (SD)] as measured by HH-DCT was 16.97 ± 2.71, by PAT 13.98 ± 2.52 and by TPXL 13.34 ± 2.68. The range of three consecutive IOP readings differed significantly between the devices [p < 0.001; mean range: 1.45 ± 1.07 (HH-DCT), 1.87 ± 0.97 (PAT) and 2.08 ± 1.77 (TPXL)]. There was no difference of the range in all devices between the ophthalmologists and the medical student (HH-DCT p = 0.68, PAT p = 0.54, TPXL p = 0.48).
  
  
  CONCLUSIONS
  IOP readings measured by HH-DCT are significantly higher than by PAT and TPXL. The differences of IOP measurements are in good accordance with previous studies using the slit-lamp-mounted DCT (SL-DCT) and Goldmann Applanation Tonometry, where SL-DCT readings were 1-3.2 mmHg higher. HH-DCT seems to give more constant results, which can be seen in the lower intra-observer variability compared to PAT and TPXL.
authors.affiliation: Department of Ophthalmology, University Hospital Zurich, Switzerland. pascal.knecht@usz.ch
authors.forename: Pascal B
authors.initials: PB
authors.lastname: Knecht
authors.forename: Ursina
authors.initials: U
authors.lastname: Schmid
authors.forename: Timo
authors.initials: T
authors.lastname: Romppainen
authors.forename: Annette
authors.initials: A
authors.lastname: Hediger
authors.forename: Jens
authors.initials: J
authors.lastname: Funk
authors.forename: Hartmut
authors.initials: H
authors.lastname: Kanngiesser
authors.forename: Christoph
authors.initials: C
authors.lastname: Kniestedt
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*; D055815:Young Adult