Effect of corneal morphometry on dynamic contour and Goldmann applanation tonometry.

Objectives

To determine the effects on dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) of the power of the flattest and steepest corneal meridians, their orientation, central corneal thickness (CCT), mean overall corneal thickness, and the mean thickness of a circular zone centered at the corneal apex of 1 mm radius (zone I) and the mean thicknesses of several concentric rings also centered at the apex of width 1 mm (zones II to VI, respectively).

Methods

A total of 136 consecutive healthy eyes were examined. Two multivariate linear regression models were constructed, 1 for each tonometry system. In both models, the predictive variables were: keratometric power of the flattest and steepest axes, flattest axis (as one of the categories 0 to 30, 30 to 60, 60 to 90, 90 to 120, 120 to 150, and 150 to 180 degrees), CCT, mean overall corneal thickness (determined using the Pentacam), and mean thicknesses of corneal zones I, II, III, IV, V, and VI (determined using the Pentacam).

Results

The multivariate regression analysis (adjusted R=0.11; P=0.04) revealed that GAT was influenced by CCT [B=0.042; 95% confidence interval (CI), 0.002-0.085] and the mean thicknesses of zones I (B=0.996; 95% CI, 0.105-1.729), II (B=-1.688; 95% CI, -3.171 to -0.204), and III (B=0.718; 95% CI, 0.028-1.407), whereas DCT was solely affected by the mean thickness of zone II (B=-0.372; 95% CI, -0.728 to -0.016) (adjusted R2=0.13; P=0.02).

Conclusions

Although DCT is only affected by the mean thickness of zone II, GAT is influenced by CCT and the mean thickness of zones I, II, and III.