title: Inter-instrument agreement and influence of central corneal thickness on measurements with Goldmann, pneumotonometer and noncontact tonometer in glaucomatous eyes.
abstract: OBJECTIVE
  This study was conducted to compare the intraocular pressure (IOP) measurements by the Goldman applanation tonometer (GAT), non contact tonometer (NCT) and the ocular blood flow (OBF) pneumotonometer in different IOP ranges in glaucomatous eyes. The effect of central corneal thickness (CCT) on IOP measurement in chronic glaucomatous eyes using the three different tonometers was also evaluated.
  
  
  METHODS
  IOP measurements of 130 eyes of primary glaucoma patients were performed using GAT by an ophthalmologist while NCT and OBF-pneumotonometer measurements were performed by an experienced optometrist. The IOP values were compared amongst the three instruments in the three different IOP ranges (0-18 mmHg, > 18 to 25 mmHg, > 25 mmHg). CCT was also measured in all patients.
  
  
  RESULTS
  The mean of paired difference between GAT and NCT was 0.9 +/- 3.1 mmHg while that between GAT and OBF-pneumotonometer was 0.3 +/- 3.4 mmHg. The OBF-pneumotonometer and NCT were more affected by corneal thickness (0.41 mmHg and 0.4 mmHg / 10 micro corneal thickness respectively) while GAT was the least affected by corneal thickness (0.3 mmHg / 10 micro corneal thickness) though the difference was not statistically significant ( P =0.42).
  
  
  CONCLUSIONS
  With appropriate correction for corneal thickness the NCT and OBF-pneumotonometer can be used as reliably as GAT in following up glaucomatous patients.
authors.affiliation: Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi - 110 029, India. gupta_v20032000@yahoo.com
authors.forename: Viney
authors.initials: V
authors.lastname: Gupta
authors.forename: Parul
authors.initials: P
authors.lastname: Sony
authors.forename: Harish C
authors.initials: HC
authors.lastname: Agarwal
authors.forename: Ramanjit
authors.initials: R
authors.lastname: Sihota
authors.forename: Ajay
authors.initials: A
authors.lastname: Sharma
mesh_terms: D000328:Adult; D000368:Aged; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D004867:Equipment Design; D005901:Glaucoma / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D007429:Intraocular Pressure; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*