title: Evaluation of a contact lens-embedded sensor for intraocular pressure measurement.
abstract: OBJECTIVE
  To evaluate a novel contact lens-embedded pressure sensor for continuous measurement of intraocular pressure (IOP).
  
  
  METHODS
  Repeated measurements of IOP and ocular pulse amplitude (OPA) were recorded in 12 eyes of 12 subjects in sitting and supine positions using 3 configurations of the dynamic contour tonometer: slit-lamp mounted (DCT), hand-held (HH), and contact lens-embedded sensor (CL). The IOP and OPA for each condition were compared using repeated measures ANOVA and the 95% limits of agreement were calculated.
  
  
  RESULTS
  The sitting IOP (mean and 95% CI) for each configuration was DCT: 16.3 mm Hg (15.6 to 17.1 mm Hg), HH: 16.6 mm Hg (15.6 to 17.6 mm Hg), and CL: 15.7 mm Hg (15 to 16.3 mm Hg). The sitting OPA for each configuration was DCT: 2.4 mm Hg (2.1 to 2.6 mm Hg), HH: 2.4 mm Hg (2.1 to 2.7 mm Hg), and CL: 2.1 mm Hg (1.8 to 2.3 mm Hg). Supine IOP and OPA measurements with the CL and HH sensors were both greater than their corresponding sitting measurements, but were significantly less with the CL sensor than the HH sensor. The mean difference and 95% Limits of Agreement were smallest for the DCT and CL sensor comparisons (0.7+/-3.9 mm Hg) and widest for the CL and HH sensors (-1.9+/-7.25 mm Hg); these wider limits were attributed to greater HH measurement variability.
  
  
  CONCLUSIONS
  The CL sensor was comparable to HH and DCT sensors with sitting subjects and is a viable method for measuring IOP and OPA. Supine measurements of IOP and OPA were greater than sitting conditions and were comparatively lower with the CL sensor. HH measurements were more variable than CL measurements and this influenced the Limits of Agreement for both sitting and supine conditions.
authors.affiliation: University of Houston College of Optometry, Houston, TX, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Twa
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Roberts
authors.forename: Huikai J
authors.initials: HJ
authors.lastname: Karol
authors.forename: Ashraf M
authors.initials: AM
authors.lastname: Mahmoud
authors.forename: Paul A
authors.initials: PA
authors.lastname: Weber
authors.forename: Robert H
authors.initials: RH
authors.lastname: Small
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D003261:Contact Lenses; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D011187:Posture; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*; D014160:Transducers, Pressure; D055815:Young Adult