title: Measurement of intraocular pressure using the NT-4000: a new non-contact tonometer equipped with pulse synchronous measurement function.
abstract: OBJECTIVE
  NT-4000 (Nidek Co. Ltd., Gamagori, Japan) is a new non-contact tonometer (NCT) equipped with pulse synchronous measurement function that can measure intraocular pressure (IOP) synchronized with the ocular pulse. The purpose of this study was to evaluate the usefulness of NT-4000 in normal subjects and in patients with glaucoma and ocular hypertension.
  
  
  METHODS
  This study included 175 eyes of 175 subjects. Firstly, the IOP was measured using NT-4000 without the pulse synchronous measurement function (NTn). Secondly, the IOP at peak, middle, and trough phases of the pulse signal were measured using NT-4000 with the pulse synchronous measurement function (NTp, NTm, NTt, respectively). Additionally, the IOP was measured with Goldmann applanation tonometer (GT). The coefficient of variation (CV) of three readings in the NCT measurements was used to evaluate the intra-session reproducibility. Statistical comparisons were performed using Wilcoxon signed rank test and one-way analysis of variance with Scheffe's test. Linear regression analysis was used to calculate correlation coefficients. P values less than 0.05 were accepted as statistically significant.
  
  
  RESULTS
  The CV of NTn, NTp, NTm, and NTt were 6.4%, 5.5%, 4.9%, and 5.2%, respectively. The CV of NTp, NTm, and NTt were significantly smaller than that of NTn (P = 0.007, P < 0.001, P < 0.001, respectively). NTp was significantly higher than NTt (P = 0.038). GT was significantly correlated with NTn, NTp, NTm, and NTt (r = 0.898, P < 0.001; r = 0.912, P < 0.001; r = 0.908, P < 0.001; r = 0.900, P < 0.001, respectively).
  
  
  CONCLUSIONS
  NT-4000 can detect the fluctuation of IOP associated with the ocular pulse.
authors.affiliation: Division of Ophthalmology and Visual Science, Graduated School of Medical and Dental Sciences, Niigata University, Niigata City, Niigata, Japan. yaoeda@med.niigata-u.ac.jp
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Yaoeda
authors.forename: Motohiro
authors.initials: M
authors.lastname: Shirakashi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fukushima
authors.forename: Shigeo
authors.initials: S
authors.lastname: Funaki
authors.forename: Haruko
authors.initials: H
authors.lastname: Funaki
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Ofuchi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nakatsue
authors.forename: Haruki
authors.initials: H
authors.lastname: Abe
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis; D012016:Reference Values; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation / Q000379:methods*