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Measuring accurate IOPs: Does correction factor help or hurt?

Pinakin Gunvant1, Robert D Newcomb, Elliot M Kirstein

  • 1Southern College of Optometry, Memphis, Tennessee, USA. contact@pinakin-gunvant.com

Clinical Ophthalmology (Auckland, N.Z.)
|July 30, 2010
PubMed
Summary
This summary is machine-generated.

Applying the Ehlers correction factor to Goldmann applanation tonometer (GAT) intraocular pressure (IOP) measurements does not improve agreement with the PASCAL dynamic contour tonometer (DCT). This correction actually worsens agreement between the two IOP measurement devices.

Keywords:
Goldmann applanation tonometercentral corneal thicknessdynamic contour tonometerintraocular pressuretonometric correction factors

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Area of Science:

  • Ophthalmology
  • Optometry
  • Biomedical Engineering

Background:

  • Intraocular pressure (IOP) measurement is crucial for glaucoma diagnosis and management.
  • Goldmann applanation tonometer (GAT) is a widely used method, but its accuracy can be affected by corneal properties.
  • PASCAL dynamic contour tonometer (DCT) offers an alternative IOP measurement, purportedly less influenced by corneal biomechanics.

Purpose of the Study:

  • To assess if the Ehlers correction factor enhances the agreement between Goldmann applanation tonometer (GAT) and PASCAL dynamic contour tonometer (DCT) intraocular pressure (IOP) measurements.
  • To determine the impact of corneal parameters on IOP readings from GAT and DCT.

Main Methods:

  • A study involving 120 participants (120 eyes) measured IOP using both GAT and DCT.
  • Central corneal thickness was measured, and the Ehlers correction factor was applied to GAT IOP readings.
  • Agreement between DCT and GAT, and DCT and Ehlers-corrected GAT IOP was analyzed using Bland-Altman plots, with stratification by race.

Main Results:

  • Mean IOP readings were GAT: 15.30 mmHg, DCT: 16.78 mmHg, and Ehlers-corrected GAT: 14.68 mmHg.
  • Bland-Altman analysis showed a wider agreement range for Ehlers-corrected GAT (-8.25 to +4.15 mmHg) compared to uncorrected GAT (-6.9 to +4.1 mmHg) with DCT.
  • Stratification by race did not alter these findings.

Conclusions:

  • The Ehlers correction factor, intended to adjust for corneal effects on GAT IOP, diminishes agreement with DCT measurements.
  • The application of this correction factor does not improve, and in fact worsens, the concordance between GAT and DCT IOP readings.
  • These results hold true irrespective of participant race.