title: Intraocular pressure measurements in relation to head position and through soft contact lenses: comparison of three portable instruments.
abstract: OBJECTIVE
  to compare the reproducibility of three portable instruments-the Tono-Pen tonometer (Reichert Ophthalmic Instruments, Depew, NY), the Phosphene tonometer (Bausch & Lomb, Rochester, NY), and the TERT (Through Eyelid Russian Tonometer; Rjazan State Instrument Making, Rjazan, Russia)-in the measurement of intraocular pressure (IOP) with and without soft contact lenses and in different head positions.
  
  
  METHODS
  twenty-six eyes of healthy volunteers were examined by the three instruments while the subjects were sitting, recumbent, and hyperextending their heads, and with and without contact lenses. IOP measurements were compared and the effects of head position and presence of contact lenses on the resultant values were analyzed.
  
  
  RESULTS
  the average difference between the recumbent and sitting positions was 3.56, 2.68, and 2.62 mm Hg for the Tono-Pen tonometer, Phosphene tonometer, and TERT, respectively. There was an increase of 5.60, 2.78, and 2.63 mm Hg in hyperextension compared to sitting for the Tono-Pen tonometer, Phosphene tonometer, and TERT, respectively. The difference in the IOP values obtained in the presence and absence of therapeutic contact lens for the three instruments in the three positions was between -1.23 and +1.47 mm Hg.
  
  
  CONCLUSIONS
  IOP measurements of bedridden patients are only slightly higher than those of sitting patients except for the Tono-Pen tonometer in the hyperextension position. The presence of contact lenses does not affect IOP values obtained by the three evaluated instruments.
authors.affiliation: Department of Ophthalmology, Tel Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel. euriya@gmail.com
authors.forename: Ainat
authors.initials: A
authors.lastname: Klein
authors.forename: Gabi
authors.initials: G
authors.lastname: Shemesh
authors.forename: Anat
authors.initials: A
authors.lastname: Loewenstein
authors.forename: Shimon
authors.initials: S
authors.lastname: Kurtz
mesh_terms: D000328:Adult; D003263:Contact Lenses, Hydrophilic / Q000706:statistics & numerical data*; D006257:Head; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*; D055815:Young Adult