title: Goldmann applanation tonometry and dynamic contour tonometry are not correlated with central corneal thickness in primary open angle glaucoma.
abstract: OBJECTIVE
  To compare intraocular pressure (IOP) measured by Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) and assess their relationship to central corneal thickness (CCT) in patients with primary open angle glaucoma (OAG).
  
  
  METHODS
  GAT, DCT, and CCT were assessed in 116 patients with OAG [mean age 65.9 (10.5); 59% female] participating in the Indianapolis Glaucoma Progression Study. GAT and DCT were measured in a randomized order followed by CCT (ultrasonic corneal pachymetry) during a single study visit. Bland-Altman plots were used to evaluate the limits of agreement between tonometery methodologies whereas multivariate regression analysis was used to evaluate the influence of CCT on GAT and DCT IOP measurements.
  
  
  RESULTS
  IOP values obtained by DCT and GAT showed a strong positive correlation in patients with OAG (r=0.93; P<0.001). Mean IOP measured with DCT [18.4 (5.1) mm Hg] was significantly higher (P<0.001) than GAT IOP measurements [16.5 (4.5) mmHg]. CCT did not seem to influence either GAT or DCT measurements (r=0.1025, P=0.16; r=0.05, P=0.46), respectively. The Bland-Altman data showed that the amount of disagreement between IOP assessment techniques varied, suggesting a proportional bias.
  
  
  CONCLUSIONS
  In this group of patients with OAG, there was a strong correlation between GAT and DCT measurements of IOP. IOP measured with DCT was consistently higher than IOP measured with GAT. Neither GAT nor DCT measurements were correlated with CCT. This data suggests that factors other than CCT may be involved in the tendency of DCT to produce higher measures of IOP than GAT.
authors.affiliation: Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, USA.
authors.forename: Guy
authors.initials: G
authors.lastname: Regev
authors.forename: Alon
authors.initials: A
authors.lastname: Harris
authors.forename: Brent
authors.initials: B
authors.lastname: Siesky
authors.forename: Yochai
authors.initials: Y
authors.lastname: Shoshani
authors.forename: Patrick
authors.initials: P
authors.lastname: Egan
authors.forename: Adam
authors.initials: A
authors.lastname: Moss
authors.forename: Miriam
authors.initials: M
authors.lastname: Zalish
authors.forename: Darrell
authors.initials: D
authors.lastname: WuDunn
authors.forename: Rita
authors.initials: R
authors.lastname: Ehrlich
mesh_terms: D000368:Aged; D003315:Cornea / Q000473:pathology*; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation*