title: Dynamic contour tonometer and Goldmann applanation tonometer performance in a developing world setting: intraocular pressure measurement acquisition and precision.
abstract: OBJECTIVE
  To examine tonometer usability and intraocular pressure (IOP) measurement precision in a general ophthalmology clinic in the developing world.
  
  
  METHODS
  A total of 100 eyes of 100 participants attending a charity ophthalmology walk-in clinic in Ghana, West Africa, had IOP measurements made with the Goldmann applanation tonometer (GAT) and the dynamic contour tonometer (DCT) in a randomized order by 2 clinicians. Both clinicians had extensive experience in using the GAT but were relatively inexperienced in using the DCT. The repeatability coefficient was calculated to determine intraobserver variability. Reproducibility of interobserver IOP measurements was calculated using Bland-Altman analysis.
  
  
  RESULTS
  IOP could not be measured in 3% of eyes using the GAT and in 16% of eyes using the DCT. The repeatability coefficient for the GAT and DCT were 2.5 and 3.0 mm Hg, respectively. The DCT repeatability coefficient was 2.3 mm Hg when only "good quality" measurements were considered. The interobserver mean difference (limits of agreement) were -0.8 mm Hg (±3.9 mm Hg) for the GAT and 0.3 mm Hg (±3.3 mm Hg) for the DCT. DCT IOP measurements were unobtainable in eyes with corneal surface irregularities or excessive eye or lid movements.
  
  
  CONCLUSIONS
  The DCT shows good measurement precision with comparable repeatability and superior reproducibility compared with the GAT. The DCT score is useful in its objectivity and improving repeatability. However, patient and ocular surface factors may impede DCT measurements, impacting upon its general usability in a high volume, walk-in community clinic.
authors.affiliation: *Glaucoma Service, Moorfields Eye Hospital NHS Foundation Trust †Churchill Medical Centre, Chingford ‡NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK.
authors.forename: Jason
authors.initials: J
authors.lastname: Cheng
authors.forename: Tahrina
authors.initials: T
authors.lastname: Salam
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Russell
authors.forename: David G
authors.initials: DG
authors.lastname: Heath
authors.forename: Aachal
authors.initials: A
authors.lastname: Kotecha
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000554:Ambulatory Care Facilities; D003906:Developing Countries; D005260:Female; D005869:Ghana; D005901:Glaucoma / Q000175:diagnosis; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult