Effect of central corneal thickness on dynamic contour tonometry and Goldmann applanation tonometry in primary open-angle glaucoma.

OBJECTIVE To compare the dependence of dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) on central corneal thickness (CCT) in primary open-angle glaucoma. METHODS In a prospective study, the interocular (right vs left eye) difference in intraocular pressure measured by DCT and GAT was compared with the interocular CCT difference in 125 patients with primary open-angle glaucoma. RESULTS Dynamic contour tonometry measurements (mean +/- SD, 19.4 +/- 4.1 mm Hg) were significantly (P=.004) higher than GAT measurements (mean +/- SD, 15.5 +/- 3.4 mm Hg), correlating significantly with each other (r(2)=0.82, P<.001). The interocular difference in intraocular pressure correlated significantly with the interocular CCT difference for GAT (r=0.30, P=.001) and DCT (r=0.23, P=.02) readings. Dynamic contour tonometry and GAT intraocular pressure differences significantly increased with older age (slope, 0.033 [95% confidence interval, 0.002-0.064] mm Hg/y; P=.03) but not with thicker CCT (slope, 0.006 [95% confidence interval, -0.003 to 0.017] mm Hg/mum; P=.22). CONCLUSIONS In this series, GAT and DCT measurements were dependent on CCT in patients with primary open-angle glaucoma. Because intraocular pressure differences between DCT and GAT were independent of CCT, DCT and GAT are susceptible to similar measurement biases depending on CCT.