Accuracy of Goldmann, ocular response analyser, Pascal and TonoPen XL tonometry in keratoconic and normal eyes


Aim: The aim of this study was to evaluate the practicality and accuracy of tonometers used in routine clinical practice for established keratoconus (KC). Methods: This was a prospective study of 118 normal and 76 keratoconic eyes where intraocular pressure (IOP) was measured in random order using the Goldman applanation tonometer (GAT), Pascal dynamic contour tonometer (DCT), Reichert ocular response analyser (ORA) and TonoPen XL tonometer. Corneal hysteresis (CH) and corneal resistance factor (CRF), as calculated by the ORA, were recorded. Central corneal thickness (CCT) was measured using an ultrasound pachymeter. Results: The difference in IOP values between instruments was highly significant in both study groups (p<0.001). All other IOP measures were significantly higher than those for GAT, except for the Goldmann-correlated IOP (average of the two applanation pressure points) (IOPg) as measured by ORA in the control group and the CH-corrected IOP (corneal-compensated IOP value) (IOPcc) measures in the KC group. CCT, CH and CRF were significantly less in the KC group (p<0.001). Apart from the DCT, all techniques tended to measure IOP higher in eyes with thicker corneas. Conclusion: The DCT and the ORA are currently the most appropriate tonometers to use in KC for the measurement of IOPcc. Corneal factors such as CH and CRT may be of more importance than CCT in causing inaccuracies in applanation tonometry techniques.

Publication DOI:
Divisions: Life & Health Sciences > Ophthalmic Research Group
Life & Health Sciences > Vision, Hearing and Language
Life & Health Sciences
Life & Health Sciences > Optometry
Additional Information: This article has been accepted for publication in British journal of ophthalmology. The definitive copyedited, typeset version Mollan, S, Wolffsohn, JS, Nessim, M, Laiquzzaman, M, Sivakumar, S, Hartley, S & Shah, S 2008, 'Accuracy of Goldmann, ocular response analyser, Pascal and TonoPen XL tonometry in keratoconic and normal eyes', British journal of ophthalmology, vol 92, no. 12, pp. 1661-1665 is available online at
Uncontrolled Keywords: Ophthalmology,Cellular and Molecular Neuroscience,Sensory Systems
Full Text Link: http://bjo.bmj. ... tent/92/12/1661
Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2008-12
Published Online Date: 2008-08-29
Authors: Mollan, S.P.
Wolffsohn, James S. ( 0000-0003-4673-8927)
Nessim, M.
Laiquzzaman, M.
Sivakumar, S.
Hartley, S.
Shah, S.



Version: Accepted Version

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