Pascal, ICare and Goldmann applanation tonometry - A comparative study

Gauti Jóhannesson*, Per Hallberg, Anders Eklund, Christina Lindén

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

56 Citations (Scopus)


Purpose: To compare intraocular pressure (IOP) measurements by Pascal, ICare and Goldmann applanation tonometry (GAT), to evaluate the effects of central corneal thickness (CCT) and curvature on IOP measurement and to estimate the intra-observer variability. Methods: A prospective, single-centre study of 150 eyes with a wide range of pressures. Six masked IOP measurements/method; corneal thickness and curvature were studied for each eye. GAT was the reference. Results: IOPPascal and IOPICare correlated with IOPGAT (r = 0.91, 0.89). Mean ICare measurement exceeded GAT by 2mmHg. Pascal measured higher than GAT at low IOPs and lower at high IOPs. For every 10mmHg increase in IOP above 31mmHg, Pascal measured 2mmHg lower than GAT and vice versa. CCT was correlated significantly with IOPGAT (r = 0.23) and IOPICare (r = 0.43) but not with IOPPascal (P = 0.12). CCT was correlated with age. In a subgroup (>50 years), ICare and the difference between IOPGAT and IOPPascal were affected significantly by the CCT, whereas IOPGAT and IOPPascal were not. Corneal curvature was correlated significantly with IOPGAT (r = -0.27) and IOPPascal (r = -0.26) but not with IOPICare (P = 0.60). Intra-observer variability within each set of six measurements was approximately 2mmHg, irrespective of method. Conclusion: This study showed a reasonable overall correlation and concordance between the IOP obtained with the three instruments. None of the methods were completely independent of the biomechanical properties of the cornea. ICare showed a significant dependency upon CCT, whereas GAT and Pascal showed a significant dependency on corneal curvature. All methods showed intra-observer variability, which leaves room for further improvement of methods.

Original languageEnglish
Pages (from-to)614-621
Number of pages8
JournalActa Ophthalmologica
Issue number6
Publication statusPublished - 2008

Other keywords

  • CCT
  • Corneal curvature
  • Dynamic contour tonometry
  • Goldmann
  • ICare
  • Intraocular pressure
  • Pascal
  • Rebound tonometry
  • Tonometry


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