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Br J Ophthalmol 2007;91:1636-1638 doi:10.1136/bjo.2007.118695
  • Extended report
    • Clinical science - Extended reports

The effect of contact lens induced oedema on the accuracy of Goldmann tonometry in a mature population

  1. K Hamilton1,2,
  2. D Pye2,
  3. S Hua2,
  4. F Yu2,
  5. J Chung2,
  6. Q Hou2
  1. 1
    Cardiff University, School of Optometry and Vision Sciences, Maindy Road, Cardiff, UK
  2. 2
    University of New South Wales, School of Optometry and Vision Science, North Wing, Rupert Myers Building, Barker Street, Sydney, NSW, Australia
  1. Kirsten Hamilton, Cardiff University, School of Optometry and Vision Sciences, Maindy Road, Cathays, Cardiff CF24 4LU, UK; hamiltonke1{at}cardiff.ac.uk
  • Accepted 11 May 2007
  • Published Online First 15 May 2007

Abstract

Aim: To determine the effect of contact lens induced oedema on the accuracy of Goldmann tonometry measurements of intraocular pressure (IOP) in mature subjects.

Methods: 22 healthy subjects aged between 50 and 60 years were recruited. Corneal curvature, IOP, and central corneal thickness (CCT) were measured before and after two hours of monocular closed eye wear of a thick hydroxyethyl methacrylate (HEMA) contact lens. Measurements were then repeated at 20 minute intervals for one hour after lens removal.

Results: Both CCT (+54.1 μm) and IOP (+2.7 mm Hg) increased significantly after lens wear (p<0.001, paired t test with Bonferroni correction). For the hour following lens removal, the measured IOP was correlated to the increase in CCT (r = 0.84, p<0.001), at a rate of 1.0 mm Hg/10 μm (95% confidence interval, 0.8 to 1.2 mm Hg/10 μm, linear mixed model analysis).

Conclusions: A relatively small increase in CCT from contact lens induced corneal oedema caused an overestimation error in Goldmann tonometry measurements of IOP in healthy mature subjects.

Footnotes

  • Competing interests: None declared.

  • Abbreviations:
    CCT

    central corneal thickness

    HEMA

    hydroxyethyl methacrylate

    IOP

    intraocular pressure

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