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Br J Ophthalmol 2004;88:518-522 doi:10.1136/bjo.2003.019331
  • Clinical science
    • Extended reports

Effect of corneal parameters on measurements using the pulsatile ocular blood flow tonograph and Goldmann applanation tonometer

  1. P Gunvant1,
  2. M Baskaran2,
  3. L Vijaya2,
  4. I S Joseph2,
  5. R J Watkins3,
  6. M Nallapothula2,
  7. D C Broadway4,
  8. D J O’Leary5
  1. 1Vision Science Group, Department of Psychological and Brain Science, University of Louisville, KY 40292, USA
  2. 2Medical Research Foundation 18 College Road, Chennai 600006 India
  3. 3Department of Optometry, University of Bradford, Bradford BD7 1DP, UK
  4. 4Department of Ophthalmology, Norfolk and Norwich University Hospital NHS Trust, Norwich NR4 7UZ, UK
  5. 5Anglia Polytechnic University, Department of Optometry and Ophthalmic Dispensing, East Road, Cambridge CB1 1PT, UK
  1. Correspondence to: Professor D J O’Leary Anglia Polytechnic University, Department of Optometry and Ophthalmic Dispensing, East Road, Cambridge CB1 1PT, UK; D.O'learyapu.ac.uk
  • Accepted 20 March 2003

Abstract

Aims: To investigate the effect of central corneal thickness and corneal curvature on intraocular pressure measurements using the pulsatile ocular blood flow tonograph and the Goldmann applanation tonometer, and to assess the agreement between the pulsatile ocular blood flow tonograph and the Goldmann applanation tonometer in intraocular pressure measurement.

Methods: 479 subjects underwent intraocular pressure measurements with the Goldmann applanation tonometer and the pulsatile ocular blood flow tonograph. Of these, 334 patients underwent additional measurement of central corneal thickness with an ultrasonic pachymeter and corneal curvature measurement with a keratometer.

Results: The intraocular pressure measurements obtained with both the Goldmann applanation tonometer and the pulsatile ocular blood flow tonograph varied with central corneal thickness and mean keratometric reading. Intraocular pressure measured using the Goldmann applanation tonometer increased by 0.027 mm Hg per µm increase in central corneal thickness. Intraocular pressure measured using the pulsatile ocular blood flow tonograph increased by 0.048 mm Hg per μm increase in central corneal thickness. For an increase of 1 mm of mean corneal curvature there was rise in intraocular pressure of 1.14 mm Hg measured by the Goldmann applanation tonometer and of 2.6 mm Hg measured by the pulsatile ocular blood flow tonograph. When compared to the Goldmann applanation tonometer, the pulsatile ocular blood flow tonograph underestimated at low intraocular pressure and overestimated at higher intraocular pressure.

Conclusion: Central corneal thickness and corneal curvature affected measurements obtained with the pulsatile ocular blood flow tonograph more than they affected measurements obtained with the Goldmann applanation tonometer.

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