Abstract

SO.04.06

Evaluation of dynamic contour tonometry in keratokonus

Schädle N., Unterlauft J. D., Klinik T., Geerling G.
Augenklinik, Universitätsklinik Würzburg

Objective: The gold standard for measuring intraocular pressure (IOP) is until now Goldmann applanation tonometry (GAT), which depends on the central corneal thickness (CCT) and curvature. In patients with keratokonus who have an abnormal corneal geometry and thickness, measurement of pressure with GAT is often difficult and not very reproduceable. We examined whether dynamic contour tonometry (DCT), a digital method to measure IOP which is adapted to the corneal geometry, is advantageous in this situation.
Methods: IOP was measured in 30 patients (19 men and 11 woman, mean age of 35±11 years) with keratokonus with GAT and DCT. In addition central corneal thickness (CCT) was measured by with the Pentacam and corneal curvature with topography. For statistical analysis the Pearson-Correlation was calculated and a Bland-Altman diagram plotted.
Results: Mean corneal thickness was 494±53 µm. Dynamic contour tonometry measured the IOP at a mean value of 14,8±2,4 mm and GAT at 12,8±3,1 mm. IOP results of GAT correlated significantly with corneal thickness (correlation coefficient -0,596, p£0,01), whereas such a correlation could not be found for the DCT (correlation coefficient -0,068).
Conclusions: The example of keratokonus confirms that IOP measured by GAT is lower than if measured by DCT. Because DCT is independent of the CCT the it may be advantageous for IOP follow-up in eyes with keratokonus, which may result in progressive corneal thinning in the long-term.

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